Bubbly Ham Casserole

1/4 C chopped onion
1/4 C butter
3 T all-purpose flour
1/2 tsp salt
dash ground nutmeg
dash pepper
2-3/4 C milk
1/4 C chopped green bell pepper
1-4 oz can mushrooms stems and pieces, drained
1-4 oz jar diced pimientos, drained
1-7 oz package macaroni, cooked and drained
1 1/2 C cubed fully cooked ham
1/2 C plus 2 T grated Parmesan cheese, divided

In a saucepan, sauté onion in butter for three minutes or until tender. Stir in flour, salt, nutmeg, and pepper. Gradually add milk, stirring constantly. Add the green pepper, mushrooms and pimientos. Bring to a boil; boil and stir for two minutes. Remove from the heat; add macaroni and mix well. Spoon half into a greased 13 x 9-inch baking pan. Sprinkle with ham and 1/2 cup Parmesan cheese. Top with the remaining macaroni mixture. Sprinkle with remaining cheese. Bake, uncovered, at 375 degrees for 20 to 30 minutes or until bubbly.