Directions:

In a large pot, cook pasta according to package directions. In a separate medium-sized pot, cook butter, onion, garlic, salt and pepper, over medium heat, until onion is slightly tender. Blend in flour and reduce heat to low, stirring constantly, until mixture is smooth and bubbly. Add milk and increase temperature to medium-high. Allow mixture to boil, stirring constantly, for 1 minute; mixture will begin to thicken. Remove from heat and stir in cheese.

In an ungreased casserole dish, layer penne with cheese sauce and stir to combine. Top with panko bread crumbs, if using. Cook, uncovered, in a 375 degree F preheated oven for 30 minutes. Garnish with parsley.