CNET

As expected, the expansion has begun.

Burger King's vegetarian Impossible Whopper debuts Monday in more than 100 stores across the San Francisco Bay Area. Before today, people who wanted to eat the fast food chain's version of the plant-based flame-grilled burger had to travel to Miami, Columbus or Montgomery.

The Impossible Whopper is made by Impossible Foods, which is known for its vegan burger that tastes a lot like real beef. Founded in 2011, the company was first to use a key ingredient called heme, a blood-like compound found in all living things and that can replicate the taste, color and aroma of meat. Other ingredients include plant-based products like soy, potato protein and coconut oil. Companies making similar meatless meat products include Beyond Meat, New Wave Foods and even Nestle.

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Burger King's goal is to offer the plant-based protein Impossible Whopper nationwide by the end of the year.

The partnership between the two companies makes sense, Impossible Foods' CEO Pat Brown said in an interview. Seeing as Burger King's massive reach with more than 17,000 locations in more than 100 countries should help him achieve his goal to "replace animals in the food system by 2035."

"Anywhere any meat product is sold globally, we want to have better products," Brown said. "A nontrivial fraction of meat sales overall are in fast food restaurants."

Impossible Burgers are now sold in more than 9,000 restaurants and chains across the US, including Umami Burger, Red Robin and White Castle. And it debuted its first meatless sausage product in select Little Caesars locations in May. The company plans to start selling its ground "beef" directly to consumers in grocery stores by the end of the year.

Impossible Foods initially focused on burgers because they're one of the most popular meat products. Brown said half of all beef sold in the US is ground beef. But that doesn't mean the company isn't exploring other animal products.

"It was a natural choice for us to start with ground beef, but in no way is that really our focus," Brown said. "We have ongoing R & D efforts to make a much wider range of products."

Proof of that? Impossible Food now has 110 scientists working in its labs at its Redwood City, California, headquarters. In the next 12 to 18 months, Brown said that number will increase by about 50%.

Originally published June 10, 3 a.m. PT.

Update, 11:11 a.m.: Adds additional information.