The Unexpected Ingredient Lidia Bastianich Uses To Upgrade French Onion Soup

Not much more than savory broth, toasted bread, melty gruyere, and, of course, sweet and rich caramelized onions make up a pot of classic French onion soup. Aside from some straightforward changes — swapping beef stock for chicken, adding herbs like bay leaves and thyme, or throwing in a pinch of sugar for caramelization — most cooks keep it simple. Lidia Bastianich's onion soup recipe is also uncomplicated, but she does add this non-traditional ingredient: mushrooms.

While you certainly won't find mushrooms in the version enjoyed by Julia Child for her final home-cooked meal, this addition actually makes a whole lot of sense. Earthy, meaty mushrooms echo the notes of the caramelized onions but also add savory depth to balance out the sweetness. They bring an undeniable dimension of umami to this simple soup, making each spoonful dynamic while still staying true to the dish's spirit.

The idea came about when Bastianich had a package of mushrooms in her fridge that she wanted to put to use. Her recipe calls for white button mushrooms, but if you don't have those, go for something similarly mild, like crimini. If you're shopping for wild mushrooms, oyster, chanterelle, puffball, and cauliflower mushrooms are also good choices. Give the onions a head start; once they're golden, add in the mushrooms and cook for another 10 minutes or so before deglazing with white wine and pouring in chicken stock.

Lidia Bastianich's empire of television shows, cookbooks, and restaurants all center around Italian cuisine, so it makes sense that her version of French onion soup would have some Italian touches as well. The changes are slight, but they result in a version of this soup that's both as comforting as the original and undoubtedly true to Bastianich's roots.

Rather than using just butter to caramelize the onions and mushrooms, Bastianich adds extra virgin olive oil to the mix as well. The rest of the touches have to do with the signature topping. Instead of something like a French baguette, Bastianich calls for an Italian loaf. To keep the bread from getting soggy in French onion soup, it's important that it's stale and toasted before topping off the bowl. A hearty variety, such as ciabatta or pane toscano, works well.

Traditionally, gruyere is the go-to cheese for French onion soup; for its Italian twist, Bastianich opts for a blend of fontina and Grana Padano. Fontina is creamy, melty, and has a pleasant pungency reminiscent of gruyere, while parmesan-like Grana Padano brings nuttiness and a deep, rich flavor.