Rich French Onion Mac and Cheese Tips, FAQ & printable recipe

Tips for success

For the best caramelization, cook the onions over medium-low heat and be patient. Stir every few minutes, and if they begin to stick, add a splash of water or wine to deglaze, scraping up the browned bits. This adds extra flavor and prevents burning. The onions are ready when they are a deep brown color and have a jam-like consistency. They will taste sweet and savory, not sharp or bitter.

To make the dish extra decadent, add a tablespoon of Dijon mustard or a splash of white wine to the cream sauce. The acidity cuts through the richness and brightens the flavor.

You can also sprinkle a little fresh thyme or chopped parsley over the top before serving for a touch of freshness. If you prefer a crispier topping, broil the dish for the last 2 minutes of baking, watching closely to prevent burning.

Variations

• Add Bacon: Cook 4 slices of bacon until crisp, crumble, and stir into the sauce before baking. The smoky flavor complements the caramelized onions and adds a salty crunch. Reduce the salt in the recipe slightly, as bacon is salty.
• Mushroom Version: Sauté 8 oz sliced mushrooms with the onions until golden and their liquid evaporates. This adds an earthy depth and makes the dish more substantial. Use a mix of cremini and shiitake for complexity.
• Spicy Kick: Add 1/2 teaspoon of red pepper flakes or a dash of hot sauce to the cream sauce. The heat balances the richness of the cheese and onions. For a smokier heat, use chipotle powder or a finely chopped chipotle in adobo.
• Herbed Croutons: Toss the croutons with 1 tablespoon of melted butter and 1 teaspoon of dried thyme or rosemary before sprinkling over the top. This adds an aromatic note that pairs well with the caramelized onions. Bake as directed.

Storage and make-ahead

Fridge

Store in an airtight container in the refrigerator for up to 3 days. Reheat gently with a splash of milk to restore creaminess.

Freezer

Freeze in a freezer-safe container for up to 2 months. Thaw overnight in the refrigerator before reheating.

Reheat

Reheat in a 350°F (175°C) oven for 15-20 minutes, or microwave in 30-second bursts. Add a splash of milk to keep the sauce creamy.

Store leftovers in an airtight container in the refrigerator for up to 3 days. The croutons will soften over time, but you can re-crisp them in the oven or toaster oven.

To reheat, place a portion in a microwave-safe dish and heat in 30-second intervals, stirring occasionally, or reheat in a skillet over medium-low heat with a splash of milk to restore creaminess. Avoid reheating in the oven for too long, as the pasta may become dry.

The caramelized onions can be prepared up to 3 days ahead and stored in the refrigerator. The entire dish can also be assembled without the croutons, covered, and refrigerated for up to 24 hours before baking. When ready to bake, add the croutons and increase the baking time by 5 to 10 minutes, since the dish will be cold. This makes it a great option for a make-ahead weeknight dinner or a holiday side dish.

Serving ideas

Serve the French onion mac and cheese hot, straight from the skillet, with a spoon that can scoop up the long cheese pulls. It pairs beautifully with a crisp green salad dressed with a simple vinaigrette to cut through the richness.

For a heartier meal, serve alongside roasted chicken or a juicy steak. The dish is also satisfying on its own, especially when topped with extra freshly ground black pepper or a sprinkle of chopped chives.

For a fun twist, serve individual portions in small ramekins, each topped with a few extra croutons. The leftovers can be scooped into lettuce cups for a low-carb option, though the pasta makes that challenging.

This mac and cheese is best enjoyed immediately, as the croutons lose their crunch over time. If you have leftovers, consider transforming them into mac and cheese balls by chilling, coating in breadcrumbs, and frying until golden.

Frequently asked questions

Recipe card

Rich French Onion Mac and Cheese

Prep 15 minCook 45 minTotal 1 hServes 6

Ingredients

• 3 tbsp butter
• 3 large yellow onions, thinly sliced
• 1/2 tsp kosher salt
• 1/4 tsp black pepper
• 1 cup heavy cream
• 8 oz medium pasta shells
• 1 1/2 cups shredded Gruyère cheese
• 1/2 cup grated Parmesan cheese
• 1 cup butter-flavored croutons

Instructions

1. Melt the butter in a large oven-safe skillet over medium heat. Add the sliced onions and salt. Cook, stirring occasionally, for 20 to 25 minutes, reducing the heat to medium-low if they brown too quickly. Continue until the onions are deep mahogany brown and very soft.
2. Season the caramelized onions with black pepper. Stir to combine and cook for another minute until fragrant.
3. Pour the heavy cream into the skillet with the onions. Stir continuously with a wooden spoon until the cream is fully incorporated and the mixture is smooth. Bring to a gentle simmer, then remove from heat.
4. Meanwhile, bring a large pot of salted water to a boil. Cook the pasta shells according to package directions until al dente. Drain well and set aside.
5. Add the drained pasta shells to the skillet with the cream and onions. Sprinkle the Gruyère and Parmesan over the pasta. Stir gently until the cheese is fully melted and the sauce is smooth and coats every shell.
6. Sprinkle the croutons evenly over the top of the mac and cheese, covering the surface completely.
7. Transfer the skillet to a preheated 375°F (190°C) oven. Bake for 15 to 20 minutes, until the croutons are golden and the edges are bubbly. Let rest for 5 minutes before serving.

Contains: gluten, milk

Estimated nutrition per serving

Calories

580

Protein

20 g

Carbohydrates

45 g

Fat

36 g

Fiber

3 g

Sugar

6 g

Sodium

700 mg

Automatic estimate from the ingredient list, not laboratory-verified.