Ingredients

• 1 pound elbow pasta
• 4 tablespoon butter
• 2 yellow onions, thinly sliced
• 3 tablespoon all-purpose flour
• 3 cup whole milk
• 8 ounce smoked gouda cheese, shredded
• 6 ounce gruyère cheese, shredded
• 2 ounce sharp cheddar cheese, shredded
• 1 teaspoon Dijon mustard
• 0.5 teaspoon salt
• 0.25 teaspoon black pepper
• 0.25 teaspoon ground nutmeg
• 1 cup panko breadcrumbs
• 2 tablespoon butter, melted, melted
• 2 tablespoon fresh parsley, chopped

Steps

1. Preheat oven to 350°F (175°C).
2. Bring a large pot of salted water to a boil and cook the elbow pasta until just al dente, about 2 minutes less than package directions (usually 6-7 minutes total).
3. Drain the pasta in a colander and set aside; do not rinse.
4. While the pasta cooks, heat 2 tablespoons of butter in a medium saucepan over medium heat.
5. Add the thinly sliced onions and cook, stirring occasionally, for 12-15 minutes until deeply caramelized and golden brown, scraping up browned bits from the bottom.
6. Remove the onions to a plate and set aside.
7. In the same saucepan, melt the remaining 4 tablespoons of butter over medium heat.
8. Whisk in the flour to create a roux and cook, stirring constantly, for 1 minute until it turns light golden.
9. Gradually whisk in the milk, starting with a small amount to avoid lumps, then add the remainder while whisking continuously.
10. Continue cooking and stirring for 4-5 minutes until the sauce thickens and coats the back of a spoon.
11. Remove from heat and whisk in the Dijon mustard, salt, black pepper, and nutmeg.
12. Add the shredded smoked gouda, gruyère, and sharp cheddar cheeses, stirring until completely melted and smooth.
13. Add the cooked pasta and caramelized onions to the cheese sauce and stir until all pasta is evenly coated.
14. Transfer the mac and cheese mixture to a 9x13 baking pan and spread evenly.
15. In a small bowl, toss the panko breadcrumbs with the 2 tablespoons melted butter and fresh parsley.
16. Spread the buttered panko mixture evenly over the top of the mac and cheese.
17. Bake for 20-25 minutes until the panko topping is golden brown and the edges are bubbling.
18. Remove from the oven and let rest for 5 minutes before serving.