Step 1

Cook pasta shells according to the package directions. Drain and set aside.

Step 2

Melt butter in a large, deep skillet over medium high heat. As soon as butter melts, add chopped onion and cook until translucent. Add garlic and cook until fragrant, about a minute. Whisk in flour. Continue whisking until flour is completely mixed in with butter. Cook for about a minute to get rid of the raw flour taste.

Step 3

Slowly add half and half, a little at a time, stirring constantly so lumps do not form. Simmer for about 3-5 minutes until mixture thickens slightly.

Step 4

While sauce is simmering, combine panko breadcrumbs, melted butter, salt, pepper and chopped parsley in a small bowl with a fork until combined and set aside.

Step 5

Add salt, pepper, garlic powder, onion powder, nutmeg and cayenne to sauce and stir to incorporate.

Step 6

Stir in the cheeses, reserving some for topping. Stir until cheese is melted and sauce is smooth. Add additional salt and pepper to taste.

Step 7

Add the cooked pasta to the pot and stir to evenly incorporate.

Step 8

Transfer the pasta mixture into a buttered 9x13 baking dish; top with remaining cheese and panko breadcrumb topping.

Step 9

Bake at 375 Degrees F° for 20-25 minutes or until golden and bubbly.