Preheat oven to 350f

Cook pasta in large pot of boiled salted water

While pasta is cooking, in a separate pot, melt the butter, whisk flour and mustard and keep it moving for 5 minutes. Make sure it's free of lumps. Stir in the milk, onion, bay leaf and paprika. Simmer for 10 minutes and remove the bay leaf.

Temper the egg. Stir in 3/4 of the cheese.

Season with salt and pepper.

Fold the macaroni into the mix and pour into a 2 quart casserole dish. Top with remaining cheese.

Melt 3 tablespoons of butter in a saute pan and toss 1 cup of panko bread crumbs to coat. Top the macaroni with bread crumbs. Bake for 30 minutes.

Remove from oven and rest for 5 minutes.