Baked Macaroni and Cheese

1/2lb. elbow macaroni
3 tbsp butter
3 tbsp. flour
1 tbsp dry mustard
3 c. milk
1/2 yellow onion, finely diced
1 bay leaf
1/2 tsp paprika
1 large egg
12 oz. sharp cheddar, shredded
1 tsp. kosher salt
pepper
TOPPING:
3 tbsp butter
1 c. bread crumbs
*Preheat oven to 350.
In a large pot of boiling, salted water, cook pasta until done. While the pasta is cooking, in a seperate pot, melt the butter. Whisk in the flour and mustard and keep it moving for about 5 min. Make sure it's free of lumps. Stir in milk, onion, bay leaf, and paprika. Simmer for about 10 min. and remove bay leaf.
Temper in 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 qt casserole dish. Top with remaining cheese.
Melt the butter in a saute pan and toss the bread crumbs to coat. Top the macaroni with the bread crumbs. Bake for 30 min. Remove from oven and rest for 5 min. before serving.