French Onion Soup Mac and Cheese takes all the deep, savory flavor of the classic soup and stirs it into a pot of creamy pasta. It’s a dish built for nights when you want something that feels both familiar and a little special.

Sweet, jammy caramelized onions melt into a rich Gruyère sauce, and a broiled cheese crust on top gives you that signature soup moment, right at the dinner table.

Why This One Stays in the Rotation

The onions take a while to cook low and slow, but that’s the only real effort. The rest comes together like a basic mac and cheese, and the reward is a dish that tastes like you spent all day on it.

What I love most is how the broth and sherry from the onions infuse the whole pot. Every bite has that unmistakable French onion flavor, with pasta standing in for the bread.

Ingredients

1 lb dried cavatappi, elbow macaroni, or other short pasta: any shape that holds sauce well
6 tbsp unsalted butter, divided: for the onions and the roux
3 large yellow onions, thinly sliced (about 6 cups): the sweet, jammy base
1 tsp granulated sugar: helps the onions caramelize
Kosher salt and freshly ground black pepper
½ cup low-sodium beef broth: adds deep savory flavor
2 tbsp dry sherry (optional): a splash of sherry tastes most authentic, but you can skip it or use balsamic vinegar
¼ cup all-purpose flour
3 cups whole milk, warmed: cold milk can make the roux seize
6 oz Gruyère cheese, grated (about 1½ cups), divided: 4 oz for the sauce, 2 oz for the topping
4 oz sharp white cheddar, grated (about 1 cup): adds creamy melt and balances the nutty Gruyère
1 tbsp fresh thyme leaves: stems removed

Variations / Substitutions

Swap Gruyère: Comté, Emmental, or all sharp white cheddar all work, though the flavor will be milder.
Skip the sherry: use 1 tablespoon balsamic vinegar or a splash of dry white wine instead.
Broth: vegetable broth can replace beef broth if you like, but the sauce won’t have quite the same savory depth.
Add a savory kick: stir 1 teaspoon of Dijon mustard into the cheese sauce before adding the cheese.
If you love the flavors of French onion soup, you might also try French Onion Chicken.

How to Make French Onion Soup Mac and Cheese

Step 1: Caramelize the Onions

Melt 4 tablespoons of the butter in a large oven-safe skillet or Dutch oven over medium heat. Add the sliced onions, a pinch of salt, and cook, stirring every few minutes, for 40 to 45 minutes until deeply golden and jammy. Meanwhile, cook the pasta in a pot of salted boiling water until just al dente; drain and set aside.

Low and slow is the key here. The onions will shrink and turn from pale to deep amber. If the pan gets dry or the onions start to catch, add a splash of water and scrape up any browned bits.

Step 2: Deglaze the Pan

Stir the sugar into the onions and cook for 2 minutes more. Pour in the ½ cup beef broth and the sherry (if using). Scrape the bottom of the pan with a wooden spoon to lift all the fond, and let the liquid simmer for about 5 minutes until it’s reduced by half.

The onions will absorb that rich, savory broth and become even more concentrated. Transfer the onion mixture to a bowl and wipe out the skillet with a paper towel so it’s ready for the sauce.

Step 3: Whisk the Cheese Sauce

Set the skillet back over medium heat and melt the remaining 2 tablespoons of butter. Whisk in the ¼ cup flour and cook for 1 minute, stirring constantly, until the paste smells nutty and the color lightens a little.

Slowly pour in the warm milk while whisking continuously to keep the sauce smooth. Bring to a gentle simmer and cook for 3 to 4 minutes, until the sauce is thick enough to coat the back of a spoon. Remove from the heat, then add the 4 oz of Gruyère and all the cheddar a handful at a time, whisking after each addition until completely melted. Stir in the thyme leaves and season with salt and a generous amount of black pepper.

Step 4: Toss the Pasta and Onions

Fold the cooked pasta and the reserved caramelized onions into the cheese sauce. Stir everything together until the pasta is evenly coated and the onions are distributed throughout.

The sauce will look a little loose now, but it tightens up under the broiler. Taste and add more salt or pepper if needed.

Step 5: Broil the Cheese Topping

Move an oven rack to the top position, about 6 inches from the broiler, and preheat the broiler to high. Sprinkle the reserved 2 oz of Gruyère evenly over the mac and cheese.

Slide the skillet under the broiler and cook for 2 to 3 minutes, watching closely, until the cheese is melted and browned in spots. Serve right away while the top is bubbly and the crust is crisp.

A Few Notes Before You Start

Keep the heat moderate when caramelizing onions; high heat burns them before they get sweet.
If you don’t have an oven-safe skillet, assemble the mac and cheese in a greased baking dish before topping and broiling.
One teaspoon of Dijon mustard added with the cheese gives a nice savory depth without tasting like mustard.
Let the dish sit for 5 minutes after broiling. It’s extremely hot straight from the oven.
For a rounder soup flavor, increase the beef broth to ¾ cup and stir in a teaspoon of Worcestershire with the onions.

If you’re cooking for a smaller crowd, halve the recipe like this:

Ingredient	Full Batch (serves 6)	Half Batch (serves 3)
Butter (divided)	6 tbsp	3 tbsp
Onions	3 large (6 cups)	1½ large (3 cups)
Pasta	1 lb	½ lb
Beef broth	½ cup	¼ cup
Sherry	2 tbsp	1 tbsp
Milk	3 cups	1½ cups
Flour	¼ cup	2 tbsp
Gruyère (divided)	6 oz	3 oz
Cheddar	4 oz	2 oz
Thyme	1 tbsp	1½ tsp

Keeping French Onion Soup Mac and Cheese Fresh

Refrigerate: store leftovers in an airtight container for up to 4 days.
Reheating: warm gently on the stovetop with a splash of milk, stirring often. The broiled crust won’t stay crisp, but a few minutes in a 350°F oven restores some of the texture.

What To Serve With This Mac and Cheese

A sharp arugula salad with lemon vinaigrette cuts right through the richness. Roasted asparagus with a squeeze of lemon also works beautifully, the brightness balancing the creamy sauce. Steamed green beans are a quick, fresh side that keeps the plate from feeling too heavy.

Frequently Asked Questions

Can I use pre-shredded cheese?

No, pre-shredded cheese is coated with anti-caking agents that prevent it from melting smoothly. Block cheese you grate yourself melts into a silky sauce.

Can I make this ahead of time?

Yes, assemble through step 4, cover, and refrigerate for up to 1 day. When ready to bake, add the reserved Gruyère and broil as directed, adding an extra minute or two since it starts cold.

What can I use instead of sherry?

Dry white wine or 1 tablespoon of balsamic vinegar both work. The balsamic adds a slightly sweeter, tangier note but still gives you that deep caramelized flavor.

Do I need an oven-safe skillet?

No, you can transfer the pasta mixture to a greased 2-quart baking dish before topping with cheese and broiling. The result is just as good.