Ham and Potato Au Gratin

2 Eggs, beaten
3 Tablespoons margarine
2 Small onions, thinly sliced
3 Tablespoons flour
2 Tablespoons olive oil
1 3/4 Cups milk
1 (10 oz) Package frozen spinach, thaw & drain
1 1/2 Cups shredded cheddar cheese
12 Ounces cooked ham, cut into strips
1/4 Cup milk
1 (24 oz) Package frozen shredded hash brown potatoes
1 Tablespoon Dijon mustard
1/4 Cup grated Parmesan cheese
1/4 Tablespoon nutmeg
1/4 Tablespoon pepper

In medium bowl beat eggs; set aside. In a large saucepan melt margarine; stir in flour. Add milk all at once. Cook and stir till bubbly; cook 1 minute more. Remove from heat. Stir 1 cup of hot mixture into beaten eggs; return mixture to saucepan. Stir in cheddar cheese, sherry and/or milk, mustard, nutmeg and pepper. Set aside.
In a large skillet cook onion in hot oil till tender, about 5 minutes. Stir in spinach; set aside. Place half of the ham in an un-greased 2 quart rectangular baking dish or casserole. Break up hash brown patties and place half atop ham. Spoon half of the cheese sauce atop potatoes. Spoon the spinach mixture atop cheese in dish. Repeat layers with remaining ham, potatoes, and sauce. Sprinkle with Parmesan cheese. Bake, uncovered, in a 350�F oven about 30 minutes; let stand 10 minutes.