Mayor de Blasio encouraged a crooked businessman to use illegal “straw donors” to funnel donations to political cronies, telling him, “I really do not want to hear. Just get it done,” the restaurateur testified Thursday.

Harendra Singh dropped the bombshells while testifying at the unrelated corruption trial of former Nassau County Executive Ed Mangano, where he’s the prosecution’s star witness.

During a meeting at Singh’s since-shuttered Water’s Edge restaurant in Queens, he told jurors, de Blasio “asked me if I can help, I believe it was Congresswoman Yvette Clarke, if I can help her.”

Singh said he told de Blasio that he could, but he’d have to use someone else to make the donation using Singh’s money.

“He said, ‘Listen, I don’t know. I don’t want to know. Just do whatever you got to do,’” Singh testified about de Blasio in Central Islip federal court.

When asked by prosecutor Catherine Mirabile to clarify what the mayor said, Singh answered: “His response was, ‘I really do not want to hear. Just get it done.’”

Singh also described a second meeting with the mayor that he said took place in the law offices of Kramer Levin Naftalis & Frankel, which defended de Blasio against corruption probes that last year were closed without any charges filed.

Singh said de Blasio asked him to make contributions to candidates running for the New York state Senate.

“I informed him, ‘It’s very hard to raise $4,950 for someone else. The only way I can do … is have somebodyu else, you know, write the check and I’ll have refunded them,’” Singh testified.

“He said, again, you know, ‘Do what ever you gotta do, but I don’t want to know.’”

Using straw donors to make campaign contributions is illegal under both state and federal law.

Prosecutors also introduced four photos into evidence showing de Blasio, then public advocate, at a fundraiser at Water’s Edge with Singh and a small group of people, including well-connected Brooklyn lawyer Ravi Batra Singh, who said he first met de Blasio when he was the city’s public advocate, didn’t specify when the meetings took place.

But de Blasio came under official scrutiny for his fund-raising efforts tied to a failed bid to help Democrats win control of the state Senate in 2014, the year after he was first elected mayor.

Singh testified that he hosted two or three fund-raising events to help de Blasio run for public advocate, and said that he twice raised $10,000.

Singh also said that de Blasio appointed him to his campaign committee when he first ran for mayor, and that he raised between $30,000 and $60,000 at three or four events.

Singh said he raised the money in “exchange of help at the Water’s Edge,” specifically “getting the lease extended” and resolving a dispute with the city over repairs to the pier.

Singh pleaded guilty in 2016 to bribing de Blasio, as part of his deal to cooperate in the case against Mangano, Mangano’s wife, Linda, and former Oyster Bay Town Supervisor John Venditto.

Venditto lawyer Marc Agnifilo said he might call de Blasio as a witness, depending on what Singh said about the mayor.

De Blasio has vehemently denied Singh’s bribery claims, saying: “This guy, to save his own skin, struck a plea deal with the federal prosecutors …he agreed to certain charges for his own self-preservation.”

Asked Thursday to respond to Singh’s testimony, de Blasio spokesman Eric Phillips said: “This administration acted appropriately at all times, as we’ve said several thousand times.”

Additional reporting by Yoav Gonen