French Onion Mac and Cheese

5 from 1 vote

Try this creamy, ultra cheesy, and delicious French onion mac and cheese next! It's perfect for a crowd and ideal for the holidays, or any time of the year. The caramelized onions add rich and deep flavors to the mac and cheese.

Prep Time30

Cook Time1 15

Total Time1 45

Course: Main Course, Side Dish

Cuisine: American

Servings: people

Calories: 618kcal

Author: Tania

Equipment

Ingredients

Caramelized onions:

4 tablespoons unsalted butter divided
4 large yellow onions peeled and sliced
2 tablespoons balsamic vinegar
2 teaspoons fresh thyme leaves
A splash of beef broth - or water only if needed

For the mac and cheese:

1 pound cavatappi pasta
½ cup unsalted butter
⅓ cup all-purpose flour
4 cups whole milk - plus more as needed
16 ounces freshly shredded Gruyere cheese divided (about 4 cups)
1 teaspoon dijon mustard
1 teaspoon garlic powder or to taste
Salt and pepper to taste

Panko breadcrumb topping

⅓ cup panko breadcrumbs
3 tablespoons olive oil

Instructions

Caramelize onions

In a large deep pan, melt 2 tablespoons of the butter over medium heat. Add the sliced onions and a pinch of salt. Cook over medium heat for 15 minutes to get a head start.
Then, lower to medium-low heat, and continue cooking the onions, stirring only occasionally, until they are caramelized deep golden, another 30 minutes. In total, caramelizing onions takes 40-45 minutes. Note: The moisture from the onions will deglaze any brown bits, but if needed, add just a little splash of broth or wine to deglaze.
During the last 5 minutes, add the remaining 2 tablespoons butter, balsamic vinegar, and thyme leaves until deglazed and golden. Set aside.

Make the mac and cheese

Preheat oven to 375 degrees F. Note: You can start making the mac and cheese about 25 minutes before the onions are ready.
Cook the pasta according to package directions until just al dente. Don’t overcook, as it will finish cooking in the oven. Drain and rinse with cold water to stop the cooking process. Set aside.
In a large pot, melt ½ cup butter over medium heat. Whisk in the flour and cook for 2-3 minutes to form a roux. It should begin to smell nutty.
Gradually stir in the milk, breaking up any lumps. It will thicken as it heats up. Season with dijon mustard, garlic powder, salt and pepper to taste.
Over low heat, stir in 3 cups of Gruyere cheese until just melted. Turn off the heat, and continue stirring until the cheese sauce is smooth. Then, add the cooked pasta into the cheese sauce, stirring to coat evenly.

Assemble and bake

Breadcrumb topping: Toss the panko breadcrumbs with olive oil. Set aside.
Transfer half of the mac and cheese into a 9x13 baking dish. Swirl in most of the caramelized onions and most of the remaining 1 cup of shredded cheese. Save some onions and cheese for the topping.
Layer on the remaining mac and cheese on top. Sprinkle the saved onions, cheese and the prepared panko mixture.
Place the mac and cheese over a large sheet pan to catch any spills, just in case. Bake uncovered in the preheated 375 F degree oven for 23-25 minutes or until bubbly and melted. Let it cool slightly before serving. Enjoy!

Video

Notes

Cook pasta until just al dente since it will all finish baking in the oven.
You need about 4 large onions. It may seem like a lot, but they will reduce significantly.
Yellow onions are best because they are milder and sweet, perfect for caramelizing. Don’t use red onions.
Use a large 12-inch deep pan for the onions. That way, they have room to cook without overcrowding, which can cause them to steam instead.
Patience is key! They need about 40-45 minutes to properly caramelize.
Grate your own cheese! This is important. Pre-shredded cheese often comes with added starches that can make the sauce gritty.

Make ahead, freezing, storage

Caramelize onions up to 2 days ahead. Refrigerate and warm slightly before using.
Or assemble, then bake later: Assemble (without the panko topping) the night before. Before baking, let sit on the counter for 30 minutes so it’s not so cold. Top with breadcrumbs, then bake as directed, adding a few extra minutes until bubbly.
Freezing: Let cool completely, then freeze in portions for up to 2 months. Thaw in the fridge overnight and reheat.
To reheat, add a splash of milk to make it creamy again.

Substitutions and variations

Cheese: Gruyere is best, but Swiss, gouda, or white cheddar work too.
Pasta: Shells, fusilli, or rigatoni.

Disclaimer: Nutritional values (per serving) are approximates only.

Nutrition