French Onion Mushroom Casserole

Do you want comfort cuisine with a chic twist? The deep, rich tastes of French onion soup are combined with soft mushrooms, caramelized onions, and melted Swiss cheese in this casserole, which is garnished with crunchy, garlicky baguette pieces. It’s the perfect casserole for a comforting supper, a substantial meal to share with loved ones, or a side dish for parties. This dish will wow and please with its layers of taste and golden cheesy topping.

Ingredients

• Olive oil for the pan
• 1¾ pounds pearl onions (click here for how to peel pearl onions)
• 8 ounces Crimini mushrooms, washed, dried, and thinly sliced
• 1½ tablespoons thyme, finely chopped
• 2 cups beef broth
• ½ cup dry red wine
• 5 tablespoons unsalted butter, softened, divided
• 2 tablespoons all-purpose flour
• 1 (approximately 2-foot) skinny French baguette, thinly sliced
• 1½ tablespoons garlic, minced, divided
• 1½ cups Swiss cheese, grated, divided
• Sea salt and freshly ground black pepper, to taste

Instructions:

1. To prepare the onions and mushrooms, heat a large pan over medium heat with a sprinkle of olive oil. Cook, stirring periodically, until the pearl onions are brown and caramelized, approximately 5 to 7 minutes. Transfer to a platter and season with a touch of salt. Add the sliced Crimini mushrooms and a little extra olive oil to the same skillet. Cook until the mushrooms are browned and have released their moisture, 5 to 7 minutes. Stir for one minute after adding the thyme.
2. Create the Sauce: Add the red wine and beef stock to the skillet containing the mushrooms. Bring to a simmer and cook for 5 to 6 minutes, reducing somewhat. Melt three tablespoons of butter in a small saucepan over medium heat. To create a roux, whisk in the flour and simmer for one to two minutes.
3. Add the roux to the mushroom sauce and stir slowly until it thickens. Return the caramelized pearl onions to the skillet and stir to combine. Add freshly ground black pepper and salt to taste.
4. Get the baguette slices ready: Set the oven temperature to 375°F, or 190°C. Line a baking sheet with the baguette slices. Add 1 tablespoon of minced garlic to the remaining 2 tablespoons of melted butter. Brush the baguette slices with the mixture. Bake until gently toasted, 5 to 7 minutes.
5. Assemble the Casserole : Pour the onion and mushroom mixture into a large casserole dish. Sprinkle half of the grated Swiss cheese over the top. Arrange the toasted baguette slices in a single layer over the casserole. Sprinkle the remaining garlic over the baguette slices, followed by the rest of the Swiss cheese.
6. Bake and Serve : Bake the casserole in the preheated oven for 15–20 minutes, or until the cheese is bubbly and golden. If desired, broil for an additional 1–2 minutes for extra crispiness. Remove from the oven, let cool for a few minutes, and serve warm. Enjoy this comforting and flavorful casserole as a main or side dish.

Conclusion:

The rich, delicious aromas of French onion soup are brought to your table in this substantial baked dish, French Onion Mushroom Casserole. The cheesy, garlicky baguette topping adds the ideal crunch, while the thick broth, earthy mushrooms, and crisp onions make a delicious basis. This recipe is perfect for big events or family gatherings because it feels both sophisticated and cozy. For a restaurant-caliber dinner at home, serve it with a glass of wine or a crisp green salad.