French Onion Soup Mac and Cheese

Why I Love This Recipe

I love this recipe because it has all the flavors of classic French onion soup but with the richness of baked mac and cheese. The caramelized onions add a deep, savory sweetness, while the Gruyère, cheddar, and Parmesan create a creamy, gooey sauce that clings to every bite of pasta. The breadcrumb topping gives it just the right amount of crunch. It’s comfort food with a gourmet twist.

Ingredients

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

• 4 large onions, sliced into rounds

• 2 tablespoons olive oil

• 2 tablespoons butter

• ¼ cup flour

• 2 ½ cups milk

• ¼ teaspoon nutmeg

• ¼ cup Parmesan cheese

• 1 block (4 oz) Gruyère cheese, shredded

• 2 cups cheddar cheese, shredded

• ¾ of the caramelized onions (reserved from cooking)

• 1 pound pasta (penne, elbow macaroni, or your choice)

• ⅓ cup breadcrumbs (for topping)

• Fresh parsley or thyme, optional for garnish

Directions

1. Caramelize the onions: I heat olive oil in a skillet over medium-low heat, add onions, and cook for about 10 minutes until softened. Then I gradually add broth a little at a time, letting it cook off each time, until the onions are deeply golden (about 30 minutes).

2. Cook the pasta: While the onions caramelize, I cook the pasta according to package directions and drain.

3. Make the cheese sauce: In the skillet, I melt butter, whisk in flour, and cook for 2–3 minutes until golden. Slowly, I whisk in the milk until thickened (3–5 minutes). I stir in nutmeg, Parmesan, Gruyère, and cheddar until smooth.

4. Combine: I mix in ¾ of the caramelized onions and the cooked pasta, tossing to coat.

5. Bake: I transfer everything into a 9×13 baking dish, sprinkle on the remaining onions, extra cheese, and breadcrumbs, then bake at 375°F for 25–30 minutes until bubbly and golden.

6. Serve: I garnish with fresh parsley or thyme for a pop of color and flavor.

Servings and timing

• Servings: 6–8

• Prep Time: 10 minutes

• Cook Time: 20 minutes (onions longer)

• Total Time: 30 minutes (plus caramelizing time)

Variations

• Vegetarian version: I use vegetable broth instead of beef broth for the onions.

• Different cheeses: I swap Gruyère for Swiss, Fontina, or Havarti for a milder flavor.

• Crunchier topping: I mix the breadcrumbs with melted butter or olive oil before baking.

• Individual portions: I bake the mac and cheese in ramekins for a dinner-party-ready presentation.

• Extra flavor: I stir in a splash of white wine while caramelizing the onions for a classic French onion soup note.

Storage/Reheating

I store leftovers in an airtight container in the fridge for up to 3 days. To reheat, I bake at 350°F until hot and bubbly, or warm individual portions in the microwave. For the best texture, I refresh the breadcrumb topping under the broiler for a couple of minutes.

FAQs

Do I need to use Gruyère cheese?

Gruyère is traditional for French onion flavors, but I can swap in Swiss, Fontina, or even mozzarella if that’s what I have on hand.

Can I make this ahead of time?

Yes, I prepare everything up to the baking step, cover, and refrigerate for up to 24 hours. I add the breadcrumbs just before baking to keep them crunchy.

What’s the secret to perfect caramelized onions?

I cook them low and slow, adding liquid (like broth or wine) in stages, and stir often. Patience makes them sweet and golden.

Can I freeze this dish?

Yes, I assemble the mac and cheese without the breadcrumb topping, wrap it well, and freeze for up to 2 months. I thaw overnight, top with breadcrumbs, and bake as directed.

What sides go well with this?

A crisp green salad or roasted vegetables balances the richness, and crusty bread is perfect for soaking up the sauce.

Conclusion

French Onion Soup Mac and Cheese is indulgent, flavorful, and the perfect mash-up of two comfort food classics. With its caramelized onions, creamy cheese sauce, and crunchy topping, it’s a dish that feels both familiar and special. Whether I serve it for a family dinner or as part of a holiday spread, it never fails to impress.

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