Washington (CNN) The Justice Department on Thursday released more than 350 pages of FBI memos from key witness interviews in the special counsel investigation into Russian interference in the 2016 US presidential election, following a Freedom of Information Act lawsuit by CNN and BuzzFeed News.

The batch includes memos about what top advisers to President Donald Trump -- including Stephen Miller, Sarah Sanders, Rob Porter, Michael Cohen, Paul Manafort and others -- told then-special counsel Robert Mueller regarding Russian interference and the President's attempts to obstruct the investigation.

The release reflects notable interviews the Justice Department showed the US House of Representatives confidentially at the conclusion of the Mueller investigation.

Here are highlights from the documents:

Why Trump did the Lester Holt interview

Trump told White House counsel Don McGahn and then deputy White House counsel Uttam Dhillon that the communications team could not get the story right about the firing of former FBI Director James Comey, so he was going to participate in an interview with NBC's Lester Holt to say what really happened, according to Dhillon's interview with investigators.

The now-infamous May 2017 interview with NBC News was the first time Trump explicitly tied the Russia probe to his rationale for firing Comey. Trump told Holt he planned to fire Comey "regardless" of a recommendation from then-Deputy Attorney General Rod Rosenstein and expressed his frustration with the bureau's investigation into Russian meddling in the 2016 election.

How Trump fired Comey

In a separate interview with investigators, White House policy adviser Stephen Miller described the process for crafting the letter that was used to fire Comey, which began over dinner at Trump National Golf Club in Bedminster, New Jersey. Trump began the dinner, which also included White House senior adviser Jared Kushner, by saying he wanted to fire Comey and articulate his reasons in a "well honed" letter. He told the group he already had a "great concept" for the letter and laid out his arguments.

Trump dictated some of the passages to Miller, who then went to research the claims and craft the document, according to Miller's interview. He added his own thoughts to Trump's and pieced a draft together.

Trump then made handwritten edits to a draft of the letter, along with Miller's own edits. The President was insistent that news of Comey's firing not leak.

Later, at a White House meeting with senior staff, including Miller, McGahn and then-White House chief of staff Reince Priebus, Trump told the group, "I'm going to read you a letter. Don't talk me out of this. I've made my decision."

Dhillon told investigators McGahn tried Trump to take out the part about the three times Comey had told the President he was not under investigation, but it seemed to be the most important part of the letter to Trump and he insisted on keeping it in.

Pre-pardons idea considered but scrapped

Trump's former lawyer and fixer Michael Cohen told the FBI at some point he and Trump attorney Jay Sekulow discussed the concept of Trump issuing "pre pardons," or pardons to everyone so that no one had to comply with the investigations.

Cohen said they learned, however, that pre-pardons would actually result in people having to cooperate with everything and that the blanket immunity of a pre-pardon would mean people would waive their right to take the Fifth Amendment against self incrimination. Cohen told the FBI he never spoke directly with Trump about pardons.

Trump Jr.: 'Is there anything you have on Hillary?'

One of the eight people in the room for the June 2016 Trump Tower Meeting, translator Ike Kaveladze, gave Mueller's investigators a vivid account of Donald Trump Jr.'s annoyance mid-way through the meeting when Trump Jr. asked: "Is there anything you have on HILLARY?"

Kaveladze recounted how the meeting was initially described to him as about adoptions, but how he later learned Trump's campaign team was promised damaging information on Hillary Clinton.

On June 6, 2016, Russian businessman Aras Agalarov, who helped setup the meeting, called Kaveladze and asked him to take part in a meeting with "someone from the Trump Organization," according to the FBI notes. Kaveladze said Aras did not provide much information, but during a second call that day, Aras asked Kaveladze if he knew anything about the Magnitsky Act. Kaveladze said he was familiar with it as it pertained to adoptions and Aras sent him a three-to-four page synopsis of the meeting topics and the business card of Nataliya Veselnitskaya.

But soon Kaveladze saw that they would be meeting with prominent members of the campaign including Trump, Jr., Jared Kushner, and Manafort and was surprised, so he called Roman Beniaminov who clarified that "Veselnitskaya had negative information on Hillary Clinton and that was the purpose of the meeting."

During the meeting, Kaveladze told investigators that "Kushner appeared to be aggravated and stressed. He was really upset and said, 'What are we doing here?'" Soon after, Trump Jr. asked for any information on Hillary Clinton.

Later, Kaveladze reported to Aras "the meeting was a complete waste of time. He told Aras the meeting was not with lawyers and they were 'preaching to the wrong crowd.'"

Mystery witness

The batch of documents raise a new mystery about the Mueller investigation: Who spoke to Mueller on April 12 and 13, 2018, for apparently several hours?

Could it be Jared Kushner? Or a witness whose name has never been publicly associated with the Mueller investigation before?

So far, the Justice Department has released public interview memos from more than 25 named witnesses who gave information to Mueller -- from former top Trump administration advisers Sarah Sanders and Miller to convicted campaign operatives Manafort and others.

But only one name is withheld entirely in the 356-page release. "Interview of [REDACTED]," one memo is titled.

According to previous CNN reporting, witnesses including Kushner spoke to Mueller in April 2018. Other top advisers were interviewed potentially around that time, or at least before April 2018.

The mystery witness spoke with special counsel's office prosecutors Jeannie Rhee and Rush Atkinson -- who had focused on the Russian interference side of the investigation and prosecutions of Michael Cohen and Roger Stone -- voluntarily over two days within Mueller's offices, according to the sliver of unredacted text in the memo.

The interview appears to be a notably long one, worth 31 pages of single-spaced notes. It only appears to reflect what the witness told Mueller's team on the first interview day, April 12, according to the document.

Aside from a brief introduction, every paragraph that the special counsel's office wrote about the mystery witness' interview is redacted. The Justice Department gives several reasons for the redactions, including personal privacy and privilege reasons.

The level of redactions in the document is especially notable, since the Mueller investigation has been relatively transparent, especially in Mueller's report, in disclosing when and which witnesses spoke to Mueller.

Extensive redactions about the details witnesses told Mueller, however, are common throughout the public records releases.

In a separate court proceeding, House Democrats revealed that they believed Kushner was interviewed by Mueller's team on April 11, 2018.

Manafort used Hannity as 'back channel' to Trump

Manafort said he used Fox News host Sean Hannity as a "back channel" to Trump in the period between the FBI raid of his apartment and his indictment months later, in October 2017.

Hannity would send supportive messages to Manafort, telling him to hang in there and that Trump had his back, according to newly released FBI interview notes.

Manafort said he didn't recall any direct or indirect communication with the White House in the period, but that Hannity, a personal friend, was "certainly a back channel."

Hundreds of messages between the two men were released in June as part of the wind-down of Manafort's criminal case in Washington, showing a close relationship and shared disdain for the Mueller investigation.

Manafort told the special counsel's investigators that he did not believe Trump will pardon him, but, as revealed in the Mueller report, Manafort was hopeful for one and noticed how the President discussed pardons publicly, according to the interview notes.

Manafort said in an interview with the investigators that he never received any assurance from the President that he would get a pardon, according to the notes.

While the President's personal lawyer Rudy Giuliani raised the prospect of a pardon for Manafort in interviews with reporters, Manafort said he hadn't talked to Giuliani since his indictment, the interview notes say.

Hannity suggested Cohen hire Sekulow

Cohen also tells the FBI that after he received a letter from the House for his testimony he contacted Jay Sekulow on the advice of Sean Hannity. Sekulow didn't take Cohen on as a client.

Cohen and Sekulow met with Trump at the White House around May 18, 2017, to get direction about how to respond to the congressional request. Cohen told Trump he replied that he would not cooperate with Congress. Trump asked him why he would respond like that, according to the FBI notes. By the end of the meeting Cohen understood the direction from Trump was to cooperate, according to the notes. The Trump Tower in Moscow did not come up during that meeting.

Cohen later spoke again with Trump, this time over the phone, about his letter response to Congress. Cohen told the FBI he didn't recall discussing specific details, only that he planned to put out a letter in response.

Cohen said he and Sekulow never discussed the disconnect between the letter contents and facts Cohen knew to be true. Cohen said he never told Sekulow that there were more than three meetings about Trump Tower Moscow but he said there was more to the story, according to the notes. Sekulow, as previously reported, told Cohen to stay on message, according to the FBI notes.

The notes add that Cohen told the FBI he never told someone whose name is redacted but could have been his lawyer based on the content of the conversation -- that he was uncomfortable with the letter. The individual whose name is redacted wrote the letter response to the House based off of Cohen's memory, according to the FBI report.

'Trump wanted them'

According to notes from an interview with Trump campaign aide John Mashburn, not only the campaign but Trump himself was interested in finding Clinton's missing emails.

"Everyone was looking for them and Trump wanted them," according to the documents. "Mashburn thought it would be great to find them so they could better understand several issues, like the Clinton Foundation, donations, etc."

Mashburn insisted that the campaign "was not scouring the Internet to try and find them. The emails they were searching for were related to Clinton's private server, and not related to the emails that WikiLeaks released."

Papadopoulos a 'problem child?'

Mashburn's interview also revealed attempts by the campaign to get rid of former Trump campaign aide George Papadopoulos, who later served 12 days in prison for lying to investigators about his contact with individuals tied to Russia during the 2016 campaign.

Mashburn and others "were aggravated with" Papadopoulos, and former Trump campaign aide and White House communications director Hope Hicks pushed for his ouster. But Mashburn thought the job should go to Sam Clovis, another campaign aide.

"At one point, Hicks told Papadopoulos to talk to Mashburn because Papadopoulos was becoming a problem child with campaign and they wanted to get rid of him," according to the documents. "Mashburn believed it was Clovis' responsibility to control Papadopoulos given that Clovis had initially brought him to the campaign."

But Mashburn's ire was specifically due to Papadopoulos' antics -- "Mashburn just wanted (Papadopoulos) to go away because he had been cold-calling embassies and using the campaign to bolster his own profile," investigators wrote.

NSC lawyer warned K.T. McFarland not to send email that could appear to be 'quid pro quo'

Long before the current Ukraine controversy, the term "quid pro quo" came up in a White House conversation between K.T. McFarland, then a deputy national security adviser, and White House lawyer John Eisenberg, according to a heavily redacted account of her interview with FBI interviewers.

The discussion in February 2017 came after national security adviser Michael Flynn, McFarland's boss, had been ousted over his interactions with the then-Russian ambassador. McFarland, who had been privy to details of Flynn's Russia conversations, was also being forced out.

McFarland was offered an ambassadorship to ease her way out of the White House. But first, Priebus had a request, McFarland told the FBI.

Priebus said words "to the effect of 'the President would like you to send me an email saying,'" the interview notes say before a redaction. The notes continue: "could she say the President never directed Flynn to call the Russians about sanctions."

McFarland told the FBI she didn't respond to Priebus's request, but called Eisenberg to recount the conversation. She told the White House lawyer that she was being fired and offered an ambassadorship, but that the letter was being requested from her.

There are additional redactions in the interview notes, but McFarland, appears to be referring to Eisenberg, saying "He offered his opinion it was a bad idea for her to write the letter because it was awkward and looked like a quid pro quo situation."

McFarland told the FBI that Priebus later came back to her and "told her not do the email and to forget he even mentioned it."

McFarland's interview, much of which is redacted, described interactions with White House officials during the transition and after inauguration as the Trump administration tried to save a possible reset of Russian relations. A top concern was Russian retaliation after the Obama administration issued sanctions following Russian interference in the 2016 elections.

McFarland told the FBI about a meeting during the presidential transition in which Trump asked her "if the Russians did it," an apparent query about the Russian hacking attacks and other activities to meddle in the 2016 election.

McFarland said she responded "yes," to the President-elect. "Trump repeated he was not sure," the interview notes say before another redaction. "He said he had reason to doubt it was the Russians."

What Manafort told Mueller on WikiLeaks

In one of the first glimpses by the public of what Manafort told Mueller, the former Trump campaign chairman described then-candidate Trump's interest in WikiLeaks email releases that Russia had stolen from the Democrats.

During the campaign, "Manafort did not want Trump distracted by the titillation of a WikiLeak's release," investigators noted about his September 2018 interview. "Manafort viewed the drops as a gift but one that they could not control."

Mueller ultimately found in his final report that the Trump campaign welcomed the WikiLeaks releases because they could damage Clinton's presidential campaign, and the campaign strategized to take advantage of them politically. But Mueller charged no one on the campaign with conspiring with the Russians.

The interview notes have several paragraphs redacted, and the publicly released version doesn't appear to add more detail about Trump's potential knowledge of efforts to reach WikiLeaks, about which Manafort's deputy had told Mueller.

Instead, Manafort offered to Mueller theories about why Trump may have publicly encouraged Russia to find Clinton's emails that summer. Manafort said he was surprised Trump had encouraged Russia specifically.

"Manafort does not know why Trump asked Russia as opposed to another country," the notes from one of Manafort's cooperation sessions said.

Manafort also gave Mueller's team a theory about why Trump named Russia when he said at a campaign rally, "Russia, if you're listening, I hope you're able to find the 30,000 emails that are missing."

"Trump would have been talking with his 'kitchen cabinet,' the investigator noted from Manafort's September 2018 interview. "Manafort guesses that more people than not were identifying Russia so that stuck in Trump's head."

Manafort ultimately lied to investigators during some of his cooperation interviews and to a federal grand jury about certain topics. He is serving seven years in prison for financial and lobbying-related crimes prosecuted by Mueller's team.

Michael Cohen and Borat?

In a redacted interview section, Cohen is shown an email referencing the Russian Union of Industrialists and Entrepreneurs. It doesn't explain the reference further but the notes indicate that while in Kazakhstan, Cohen met with someone who stormed out of the room after Cohen gave him his business card.

A few minutes later the person returned, angry, and asked Cohen if he was related to Sasha Baron Cohen, the comedian who played Borat, a fictitious Kazakh journalist, in a satire. Cohen said after the election he had no meetings or contemplation of securing Russian investment money.