Greek Pastitzio

1 pound hamburg
1 cup chopped onion
3/4 cup peeled and chopped tomatoes
1-1/2 teaspoons freshly ground black pepper
1/2 teaspoon oregano
1/2 cup grated Gruyere cheese
1 pound small elbow macaroni, cooked and drained

Saute onion and meat in oil until meat is brown. Stir in tomatoes, salt, pepper and oregano, simmer 5 minutes. Stir in cheese.

Sauce:
2 tablespoons butter
1/2 teaspoons salt
1 tablespoon flour
1/8 teaspoon pepper
1 cup milk
1 egg yolk
1/4 cup grated parmesan cheese

For sauce, melt butter in pan over low heat, gradually blend in flour, salt and pepper. Add warm milk gradually stirring constantly until mixture comes to a boil. Cook on low heat 5 minutes. Beat egg yolk and grated cheese in small bowl. Slowly add a small amount of the hot mixture to the egg stirring constantly, then add this back to the pan.

Grease a 2 quart casserole dish. Place half of the macaroni in the casserole. Cover with meat sauce. Add remaining macaroni. Pour sauce over the macaroni. Bake 350 degrees for 30 minutes until light brown on top..