Preheat oven to 375°.
Place a large saucepan coated with cooking spray over medium-high heat until hot. Add ham; sauté 2 minutes or until lightly browned. Remove from pan; set aside.
Combine milk and broth in pan; bring to a boil, stirring constantly. Stir in grits; reduce heat, and simmer 7 minutes or until thick, stirring frequently. Combine grits mixture, ham, cheese, garlic powder, pepper, and spinach in a large bowl. Stir well; set aside.
Beat egg whites at high speed of a mixer until stiff peaks form. Gently fold one-fourth of egg whites into grits mixture; gently fold in remaining egg whites. Spoon mixture into a 2-quart casserole or soufflé dish coated with cooking spray. Bake at 375° for 40 minutes or until set and lightly browned.
Note: Substitute cured ham or cooked smoked pork chops for country ham, if desired.