French Onion Mushroom Casserole
With a crispy, golden breadcrumb crust on top, French Onion Mushroom Casserole is a hearty, savory dish that combines the rich flavors of caramelized onions, earthy mushrooms, and a creamy, cheesy sauce. This casserole is a delicious, filling side dish or vegetarian main course that combines the finest of two well-loved classics: French onion soup and mushroom dishes. This casserole will quickly become a staple in your recipe repertoire and is ideal for comforting evenings, holiday feasts, or any time you’re in the mood for a rich, savory treat!
Ingredients:
1 tablespoon olive oil
2 tablespoons butter
1 medium onion, thinly sliced
2 cups mushrooms, sliced (preferably a mix of cremini and white mushrooms)
3 cloves garlic, minced
1 teaspoon dried thyme (or 2 teaspoons fresh thyme)
Salt and pepper to taste
1 cup vegetable or chicken broth
1/2 cup heavy cream
1/2 cup grated Gruyère cheese (or Swiss cheese)
1/4 cup grated Parmesan cheese
1/2 cup breadcrumbs (panko or regular)
1 tablespoon fresh parsley, chopped (for garnish)
Instructions:
Preheat the oven to 375°F (190°C). Grease a 9×9-inch baking dish with a little butter or cooking spray.
Cook the onions:
In a large skillet, heat the olive oil and butter over medium heat.
Add the sliced onions, and cook for about 15-20 minutes, stirring occasionally until they become golden brown and caramelized.
Cook the mushrooms:
Add the sliced mushrooms and minced garlic to the skillet with the onions.
Stir in the thyme, salt, and pepper, and cook for another 8-10 minutes until the mushrooms release their moisture and soften.
Prepare the sauce:
Once the mushrooms have softened, pour in the vegetable or chicken broth and bring it to a simmer.
Add the heavy cream, and let the mixture simmer for about 5 minutes to thicken slightly. Taste and adjust the seasoning as needed.
Combine everything:
Pour the mushroom and onion mixture into the prepared baking dish.
Sprinkle the Gruyère and Parmesan cheeses over the top.
Make the topping:
In a small bowl, combine the breadcrumbs with a tablespoon of melted butter (this helps the breadcrumbs brown nicely).
Sprinkle the breadcrumbs evenly over the casserole.
Bake:
Place the casserole in the oven and bake for 20-25 minutes, or until the cheese is bubbly and the breadcrumb topping is golden and crispy.
Garnish and serve:
Remove the casserole from the oven, and sprinkle fresh parsley on top for a burst of color and flavor.
Serve hot, and enjoy!
Tips:
For extra flavor, you can add a splash of white wine to the onions and mushrooms while they cook.
You can make this dish ahead of time and refrigerate it. Just bake it right before serving.
For a vegan version, substitute the heavy cream with coconut cream and use vegan cheese options.