French Onion Chicken Bake

This French Onion Chicken Bake takes all of your favorite flavors from a classic bowl of French onion soup and turns them into a hearty casserole!

Course Dinner

Cuisine American

Keyword french onion baked chicken, french onion chicken bake, french onion chicken casserole

Prep Time 10

Cook Time 30

Total Time 40

Servings people

Calories 450kcal

Author Blair Lonergan

2 tablespoons salted butter
1 lb. Vidalia onions, or other sweet onions, thinly sliced (about 2 medium onions)
Kosher salt and ground black pepper, to taste
1 teaspoon minced fresh thyme leaves (or about ¼ teaspoon dried thyme)
1 clove garlic, peeled and minced or pressed
1 tablespoon balsamic vinegar
1 teaspoon Worcestershire sauce
3 cups cooked, diced or shredded chicken (such as the meat from a rotisserie chicken)
1 cup chicken stock or beef broth
9 slices crusty French baguette (or other similar bread), sliced about ½-inch thick
1 cup grated Gruyere cheese (or sub with grated Swiss cheese)
Optional, for serving: chopped fresh thyme or parsley for garnish

Preheat oven to 475°F. Arrange the bread slices on a baking sheet and toast lightly in the oven, about 4-5 minutes. Set aside.
Meanwhile, in a medium ovenproof skillet, melt butter over medium-high heat. Add the onions and season with salt and pepper. Cover with a lid and cook, stirring occasionally, until the onions are softened, about 3-5 minutes.
Remove the lid, stir in the thyme and garlic, and continue to cook and stir until the onions are deep golden brown, about 15 minutes. As the onions cook, add a tablespoon of water; stir. Once the water evaporates, repeat the process with additional tablespoons of water. This prevents the onions and garlic from burning, and it speeds up the caramelization.
Add the vinegar and Worcestershire sauce; cook for 1 more minute.
Stir in the chicken and broth; taste and season with salt and pepper. Bring the mixture to a boil, then remove from the heat.
Turn the oven to “BROIL.”
Arrange the toasted bread slices on top of the chicken and onion mixture. Sprinkle the cheese over top.
Place the skillet under the broiler for about 3-5 minutes, until the cheese melts and starts to brown.
Garnish with chopped fresh parsley or thyme, if desired.

I use this 2.25-quart Le Creuset braiser, which is an oven-safe skillet with a lid. A 9-inch or 10-inch cast iron skillet will also work well.
Stir the onions regularly and add water frequently to ensure that the onions don't burn. If they start to get too dark too quickly, just lower the temperature and cook them over medium heat or medium-low heat.
Choose a high-quality crusty bread (such as a French baguette) for topping your casserole. It only needs to be toasted lightly, because it will go under the broiler and get even darker and crispier on the edges.
Keep a close eye on the dish while it’s under the broiler, since the bread and cheese can burn quickly.
Garnish each serving with fresh herbs for a bright, colorful touch. Good options include thyme, parsley, rosemary, or chives.