Before "cream of" soups were the go-to ingredient for adding moisture to your casseroles, there was béchamel sauce, the bland but creamy roux-thickened milk sauce.
While working on the book Cauliflower, published by Short Stack Editions, I discovered that steamed cauliflower puréed with a little vegetable broth is a dead ringer for béchamel. In fact, I started calling it "fauxchemel."
In the book, I whisk fauxchemel with cheese to make a fondue and a topping for moussaka. But this time of year, Serious Eats focuses on vegan recipes, so I wanted to explore how fauxchemel would stand up without cheese in a plant-based casserole.
Green bean casserole seemed like the perfect test subject. It’s beloved, even by most food snobs. The classic recipe most of us know relies on canned cream of mushroom soup, so my first order of business was to try to create a vegan version.
For the creamy base, I puréed steamed cauliflower with broth for my fauxchemel. I decided to finely chop the mushrooms, along with some onions, in a food processor. This, I reasoned, would help the flavor permeate the casserole without giving you overly large bites of mushroom—it’s green bean casserole, not mushroom casserole. While this technique turns the sauce a bit beige, the flavor benefits are worth it. (If you want, you can also crush the mushrooms first, as Kenji does in his classic green bean casserole recipe, to simulate even more accurately the texture of the mushroom bits in the canned soup.)
The canned soup gets boosts of flavor from dehydrated garlic and MSG; in this recipe, garlic powder and nutritional yeast help bring in a savoriness that's similar to the one we're all used to. Because I love a bright note with rich dishes, I also add lemon zest, but you’re welcome to leave it out if it's too much of a departure from the original casserole's flavor profile.
Finally, for the classic onion topping, I fry my own red onions, but I won’t tell if you use the canned ones. They’re vegan, after all.