French Onion Soup Mac & Cheese

Why You’ll Love This Recipe

I love how this dish transforms two comfort food favorites into something totally new. The caramelized onions bring a slow-cooked sweetness that balances the richness of the cheese sauce, while the Gruyère adds that unmistakable French onion soup flavor. It’s creamy, flavorful, and finished with a perfectly crispy Parmesan topping. Whether I’m making this for a family dinner or bringing it to a potluck, it always gets rave reviews.

Ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

Pasta & Onions:
12 ounces elbow macaroni
3 large yellow onions, thinly sliced
2 tablespoons olive oil
3 tablespoons butter (divided)
2 cloves garlic, minced
1 teaspoon fresh thyme (or ½ teaspoon dried)

Cheese Sauce:
3 tablespoons all-purpose flour
2 cups vegetable broth
2 cups whole milk
½ cup heavy cream
2 cups Gruyère cheese, shredded
1 cup sharp cheddar cheese, shredded
1 cup mozzarella cheese, shredded
1 teaspoon salt
½ teaspoon black pepper

Topping:
1 cup breadcrumbs
½ cup grated Parmesan cheese

Directions

1. Preheat Oven

I start by preheating the oven to 375°F (190°C) and buttering a large baking dish.

2. Caramelize the Onions

In a large skillet, I heat the olive oil and 1 tablespoon of butter over medium heat. I add the sliced onions and cook slowly, stirring often, for 25–30 minutes until deeply golden and caramelized. Then I stir in the garlic and thyme and cook for another minute.

3. Cook the Pasta

While the onions are cooking, I boil the macaroni in salted water until just al dente, then drain and set it aside.

4. Make the Roux and Sauce

In a large pot, I melt the remaining 2 tablespoons of butter. I whisk in the flour and cook for 1 minute to form a roux. I slowly whisk in the vegetable broth, then the milk and cream, stirring until the mixture is smooth and begins to thicken.

5. Add the Cheese

I reduce the heat to low and stir in the Gruyère, cheddar, and mozzarella until melted and creamy. I season with salt and black pepper.

6. Combine Everything

I fold the cooked macaroni and caramelized onions into the cheese sauce until everything is evenly coated.

7. Assemble and Top

I transfer the mac and cheese mixture to the prepared baking dish. In a small bowl, I combine the breadcrumbs with the grated Parmesan, then sprinkle it evenly over the top.

8. Bake

I bake the dish uncovered for 20–25 minutes, until bubbly and golden on top. Then I let it rest for 5 minutes before serving.

Servings and timing

This recipe makes 6 servings and takes about 1 hour total:
Prep time: 15 minutes
Cook time: 45 minutes

Variations

Sometimes I mix in sautéed mushrooms or chopped spinach for an earthy twist. For extra crunch, I toss the breadcrumbs with a drizzle of olive oil before baking. If I want it a bit spicier, I add a pinch of crushed red pepper or a few dashes of hot sauce to the cheese sauce. And when I’m feeling really decadent, I top it with crispy fried onions before serving.

Storage/reheating

I store leftovers in an airtight container in the fridge for up to 3 days. To reheat, I bake it in a 350°F (175°C) oven until warmed through, or microwave individual portions. If the sauce thickens too much, I stir in a splash of milk when reheating.

FAQs

Can I use a different type of pasta?

Yes, I’ve made this with shells, cavatappi, and penne. Any short, sturdy pasta works well.

What’s the best cheese substitute for Gruyère?

Swiss cheese or Emmental are good alternatives. For a sharper flavor, I sometimes use Fontina or a mix of Swiss and provolone.

Can I caramelize the onions in advance?

Absolutely. I often caramelize the onions a day ahead and store them in the fridge to save time.

Is this recipe freezer-friendly?

It freezes okay, but I prefer to freeze it unbaked. I assemble the dish, cover tightly, and freeze. When I’m ready, I thaw and bake as directed.

What can I serve this with?

It’s great with a simple green salad, roasted vegetables, or even as a side to grilled meats or veggie burgers.

Conclusion

French Onion Soup Mac & Cheese is the ultimate cozy fusion recipe—sweet, savory, cheesy, and irresistibly creamy. With the richness of classic mac and cheese and the deep flavor of caramelized onions, it’s a dish that feels both familiar and special. I love making it for gatherings, holiday meals, or whenever I need serious comfort food.

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