Ingredients:
3 tablespoonsextra-virgin olive oil
3 large yellow onions (about 1½ pounds), thinly sliced
1/2 teaspoonkosher salt, plus more to taste
2 1/2 cupshot vegetable, turkey, or chicken stock, plus more as needed
2 tablespoonsall-purpose flour (or 1 tablespoon cornstarch)
Freshly ground black pepper, to taste
Directions:
Heat the oil in a wide skillet over medium-high heat. Add the onions and salt and cook for about 20 minutes, stirring occasionally and lowering the heat as needed to prevent burning. After 20 minutes, the onions should be soft and translucent, with a light amber color.
Increase the heat to medium, then gradually incorporate 1 cup of the stock: Add a splash to deglaze the pan, then cook down until the stock has mostly evaporated. Repeat this until you have incorporated the 1 cup of stock and the onions are soft and sort of mushy, with a dark amber color.
Using a fork, mix the flour or cornstarch with ¼ cup of hot water in a bowl. Using a fine-mesh sieve, strain the mixture over the onions to prevent any clumps in the sauce. Vigorously stir to incorporate and cook for about 1 minute to remove the raw flour/starch taste. While stirring, slowly add the remaining 1½ cups of stock to the onions. Bring the sauce to a simmer and cook until it’s as thick as you like. (If the gravy becomes too thick, you can add more stock to loosen it up.)
Season with black pepper to taste and salt if needed. This gravy can be made ahead—simply store in an airtight container in the fridge and reheat in a pot right before serving.