preheat oven to 350°F.

in a large pot of boiling, salted water cook the pasta to al dente.

while the pasta is cooking, in a seperate pot, melt the butter. sweat onions with bay leaf.

whisk in the flour, paprika and mustard and keep it moving for about five minutes. make sure its free of lumps. stir in the milk.

while still stirring consistently, simmer for ten minutes then remove the bay leaf

whisk the egg in a seperate bowl and slowly pour the egg into the milk mixture. (this process is called tempering.)do not stop stirring. make sure your eggs dont scramble. stir in 3/4 of the cheddar 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 the butter in a saute pan and toss the bread crumbs to coat. top the macaroni with the bread crumbs. bake for 30 minutes. remove from oven and rest for five minutes before serving.