salsa, sour cream, and additional green onions for serving
In a medium bowl stir together ham, green onions and 2 cups of cheese (save the remaining 1/2 cup for later). Spray a 9x13 inch baking dish with cooking spray. Use a 1/3-cup measuring cup to scoop out cheese mixture onto a tortilla. Roll up tortilla and place seam side down in the baking dish. Roll up all tortillas and place them into the baking dish with the sides touching.
Whisk together half-and-half, eggs, salt, and flour. Pour over tortillas. Cover and refrigerate overnight.
In the morning, preheat oven to 350º. Bake covered for 30-40 minutes. Remove foil and sprinkle remaining 1/2 cup of cheese over enchiladas. Bake for 10 more minutes or until tops are golden brown and the egg mixture is set.
Serve with salsa, sour cream, and additional green onions.