French Onion Mac and Cheese Recipe

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

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

1. In a large deep pan, melt 2 tablespoons of butter over medium heat. Add the sliced onions and a pinch of salt. Cook for 15 minutes stirring occasionally to start the caramelizing process. Then reduce heat to medium-low and continue cooking, stirring occasionally, until onions are deep golden brown and caramelized, about 30 more minutes. Add a splash of broth or water if needed to deglaze the pan. During the last 5 minutes, add the remaining 2 tablespoons butter, balsamic vinegar, and thyme leaves, stir well, then remove from heat and set aside.
2. Preheat the oven to 375 degrees Fahrenheit. You can start preparing the mac and cheese about 25 minutes before the onions are done.
3. Cook the cavatappi pasta according to package directions until just al dente. Drain and rinse under cold water to stop the cooking process, then set aside.
4. In a large pot, melt ½ cup butter over medium heat. Whisk in the flour and cook for 2-3 minutes until it forms a roux and begins to smell nutty. Gradually whisk in the milk, stirring constantly to avoid lumps. Heat until thickened. Season with Dijon mustard, garlic powder, salt, and pepper to taste.
5. Reduce heat to low and stir in 3 cups of shredded Gruyere cheese until just melted and the sauce is smooth. Turn off the heat. Stir in the cooked pasta until everything is evenly coated.
6. In a small bowl, toss the panko breadcrumbs with olive oil and set aside.
7. In a 9×13 baking dish, spread half of the mac and cheese. Swirl in most of the caramelized onions and most of the remaining 1 cup of Gruyere cheese. Top with the remaining mac and cheese. Sprinkle the remaining caramelized onions, cheese, and the prepared panko breadcrumb mixture evenly on top.
8. Place the baking dish on a large sheet pan to catch any spills. Bake uncovered at 375 degrees Fahrenheit for 25 minutes, or until the top is bubbly, golden, and melted. Allow to cool slightly before serving.

Notes

• Cook pasta until just al dente as it will continue cooking in the oven.
• Use 4 large yellow onions for best flavor; they reduce significantly when caramelized.
• Yellow onions are ideal due to their mild sweetness; avoid red onions.
• Use a large 12-inch deep pan for caramelizing to avoid overcrowding and steaming.
• Patience is key for perfect caramelized onions, requiring about 40-45 minutes of cooking.
• Grate your own Gruyere cheese for a smooth sauce; pre-shredded cheese can contain starches that cause grittiness.
• Caramelized onions can be prepared up to 2 days ahead and warmed before using.
• Assemble the dish (without breadcrumbs) the night before; bring to room temperature before baking and add breadcrumbs just before baking.
• Freeze leftovers after cooling for up to 2 months. Thaw overnight in the fridge and reheat with a splash of milk to restore creaminess.
• Substitute Gruyere with Swiss, gouda, or white cheddar cheese if desired.
• Alternative pasta shapes like shells, fusilli, or rigatoni can be used.