Colleen's Mac n' Cheese

Ingredients:
1/2 pound penne pasta
1/2 cup butter
3 Tbsp minced fresh onion
1/2 tsp pepper
1/2 Tbsp flour
2 Tbsp Dijon Mustard
1 1/2 cup milk
1 pound grated Gruyere cheese (usually a block)
1 pound grated extra sharp Cheddar cheese (usually a block)
1 cup grated Parmesan cheese + 1/2 cup more for topping
1/2 cup Panko bread crumbs

Instructions:
Heat oven to 350F
Make pasta per usual on stove top
Melt butter in large pot over medium heat and add onion. cook for 2 minutes, add pepper and flour.
Cook stirring constantly for 3-4 minutes. don't let flour brown.
Add mustard and milk and bring to a simmer.
Simmer for 10-15 minutes. sauce will thicken. if too thick add more milk.
Once the sauce has simmered for at least 10 minutes, add the Cheddar, Gruyere cheese and 1 cup of Parmesan cheese.
Shut off heat and stir them until combined.
Toss pasta into the cheese sauce until pasta is covered.
Place pasta in an 11 x 14 inch glass or ceramic baking dish*.
Sprinkle with remaining Parmesan cheese.
Sprinkle with panko bread crumbs.
Bake for 40 minutes or until top is golden and toasted.

Notes:
1. I normally cook for 35ish minutes then put on broil until golden brown.
2. I add any other cheese I might have on hand at the time..pecorino romano, manchego, monterey jack, etc.. the more cheese the better, in my opinion
3. You can use any size dish to bake it in as long as it is 2 to 3 inches deep, I have made them in 4" round ramekins and had the same results
4. For a spicy version, julienne 2 jalapeno or other hot peppers and add to mixture before baking