Why does my mac and cheese sauce feel gritty or oily?

This often happens when the cheese is added to a sauce that is too hot, causing the fat and protein to separate. Always remove the béchamel (milk/roux base) from the heat before stirring in the grated cheese slowly. Also, ensure you are grating cheese from a block, as pre-shredded varieties contain starches that make melting difficult.

Can I substitute the Gruyère cheese?

Yes, but you will lose some of the signature French Onion flavor. The closest substitutes are Comté or high-quality Swiss cheese, though they may be slightly less complex. If you cannot find Gruyère, use a little extra sharp Cheddar combined with a touch of aged Provolone for depth.

What is the best pasta shape for this recipe?

Any short, sturdy pasta shape with ridges or tubes works best, as they trap the thick, rich sauce and onions beautifully. Cavatappi, elbow macaroni, shells, or even fusilli are excellent choices. Avoid long, thin strands.

Can I use vegetable broth instead of beef broth?

Absolutely. While traditional French onion soup often uses beef broth for depth, vegetable broth works perfectly well, especially if you are serving this as a vegetarian side. The key is ensuring the broth is high quality and concentrates the savory flavors as you deglaze the onions.

French Onion Mac and Cheese: The Ultimate Tested Homemade Recipe

The Ultimate, Tested French Onion Mac and Cheese Recipe

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Our ultimate, tested homemade French Onion Mac and Cheese recipe expertly combines creamy Gruyère-Cheddar sauce with slow-cooked, deeply savory caramelized onions and a crunchy panko topping.

Author: Emily Parker
Prep Time: 25 mins
Cook Time: 70 mins
Total Time: 1 hour 35 mins
Yield: 8 servings 1x
Category: Main Dish, Casserole
Method: Baking
Cuisine: American, French

Ingredients

Scale

4 medium Yellow Onions, thinly sliced

2 tbsp unsalted butter (for onions)

1 tsp fresh thyme leaves

1/2 tsp kosher salt (for onions)

1/4 cup vegetable or beef broth

1 pound dry pasta (cavatappi or shells)

1/2 cup (1 stick) unsalted butter (for roux)

1/2 cup all-purpose flour

4 cups whole milk, warmed

1 tsp Dijon mustard

1/2 tsp black pepper, 1/4 tsp nutmeg

8 oz. Gruyère cheese, freshly grated

8 oz. Sharp White Cheddar, freshly grated

Salt to taste

2 tbsp unsalted butter, melted (for topping)

1 cup panko breadcrumbs

1/4 cup grated Parmesan cheese

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Instructions

1. Melt 2 tbsp butter in a large pot over medium-low heat. Add onions, 1/2 tsp salt, and thyme. Cook until dark golden brown, about 45–60 minutes.

2. Pour in the 1/4 cup broth and scrape up any browned bits. Remove onions and set aside.

3. Cook pasta until al dente. Drain and set aside.

4. In the same pot, melt the remaining 1/2 cup butter. Whisk in 1/2 cup flour and cook for 1–2 minutes.

5. Gradually whisk in the 4 cups of warm milk. Bring to a simmer, stirring until thickened. Remove from heat.

6. Whisk in Dijon, pepper, and nutmeg. Add Gruyère and Cheddar gradually, stirring until smooth.

7. Gently fold in the cooked pasta and most of the caramelized onions.

8. Transfer to a buttered 9×13-inch baking dish. Top with panko, Parmesan, and melted butter.

9. Bake at 375°F for 20 minutes, or until bubbling and golden. Let cool for 10 minutes before serving.

Notes

For the smoothest sauce, always grate your own cheese from the block.

This dish can be prepped up to 24 hours ahead, but add the topping just before baking.

Reheat leftovers in the oven with a splash of milk or broth to prevent dryness.

Nutrition

Serving Size: 1 bowl
Calories: 650
Sugar: 8g
Sodium: 650mg
Fat: 33g
Saturated Fat: 20g
Unsaturated Fat: 8g
Trans Fat: 0g
Carbohydrates: 55g
Fiber: 3g
Protein: 35g
Cholesterol: 105mg

Find it online: https://www.flavourrecipe.com/french-onion-mac-and-cheese/