Description

This French Onion Soup Mac & Cheese combines the rich, caramelized flavors of traditional French onion soup with the comforting creaminess of classic mac and cheese. Featuring a luscious blend of Gruyère, sharp cheddar, and mozzarella cheeses, topped with crispy Parmesan breadcrumbs, this baked casserole is a hearty and flavorful dish perfect for family dinners or special occasions.

Ingredients

Scale

Pasta

12 ounces elbow macaroni

Onion Soup Base

3 large yellow onions, thinly sliced
2 tablespoons olive oil
3 tablespoons butter (divided)
2 cloves garlic, minced
1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried thyme)

Sauce

3 tablespoons all-purpose flour
2 cups vegetable broth
2 cups whole milk
1/2 cup heavy cream
2 cups shredded Gruyère cheese
1 cup shredded sharp cheddar cheese
1 cup shredded mozzarella cheese
1 teaspoon salt
1/2 teaspoon black pepper

Topping

1 cup breadcrumbs
1/2 cup grated Parmesan cheese

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Instructions

Preheat and Prepare: Preheat the oven to 375°F (190°C) and butter a baking dish thoroughly to prevent sticking.
Caramelize Onions: Heat olive oil and 1 tablespoon of butter in a skillet over medium heat. Add the sliced onions and cook, stirring frequently, until they are deeply caramelized and golden brown, about 25 to 30 minutes. Stir in the minced garlic and thyme leaves for added flavor.
Make the Roux and Sauce: Add the remaining 2 tablespoons of butter to the skillet. Stir in the flour to form a roux and cook for 1-2 minutes to eliminate the raw flour taste. Gradually whisk in the vegetable broth, then the milk and heavy cream, continuing to whisk until the mixture is smooth and thickened.
Add Cheeses and Seasoning: Stir in the shredded Gruyère, sharp cheddar, and mozzarella cheeses slowly until they are fully melted and the sauce is creamy. Season the sauce with salt and black pepper to taste.
Combine Pasta and Onion Sauce: Toss the cooked al dente elbow macaroni in the cheesy onion sauce ensuring each piece is well coated with the flavorful mixture, including the caramelized onions.
Assemble in Baking Dish: Transfer the cheesy pasta mixture into the prepared baking dish. Mix the breadcrumbs and grated Parmesan cheese together, then evenly sprinkle this topping over the casserole.
Bake: Bake uncovered for 20 to 25 minutes, or until the topping is golden brown and the casserole is bubbly throughout.
Rest and Serve: Remove from oven and let the mac & cheese rest for 5 minutes to set. Garnish with fresh thyme if desired, then serve hot.

Notes

Caramelizing onions properly is key to developing the deep French onion flavor—do not rush this step.
You can substitute vegetarian-friendly vegetable broth for beef broth to keep the dish vegetarian.
For a gluten-free option, use gluten-free flour and breadcrumbs.
If you don’t have fresh thyme, dried thyme works as well; just use half the amount.
Use freshly shredded cheese rather than pre-shredded for better melting and texture.