Preheat oven to 350 degrees F (180 degrees C).
In a large pot, bring Water (4 cup) to a boil over medium to high heat. Add Salt (1 teaspoon) and Quick Cooking Grits (1 cup) and return to a boil. Reduce heat to low and cook grits 3 to 5 minutes, stirring often, until thickened. Set aside.
In a large skillet, melt Butter (4 tablespoon). Add Mirepoix (18 ounce) to butter and saute over low to medium heat until softened. Remove sautéed vegetables to a bowl and set aside.
In the same skillet, melt Butter (4 tablespoon) over medium heat and stir in All-Purpose Flour (3 tablespoon). Cook and stir, until mixture is bubbly. Add Milk (1 1/2 cup) and cook until sauce thickens. Stir in Shredded Cheddar Cheese (2 cup), Canned Mild Diced Green Chiles (4 ounce) and sautéed vegetables. Season with Salt and Pepper (to taste).
Pour grits mixture into 9-inch by 13-inch by 2-inch baking dish that has been sprayed with Nonstick Cooking Spray (to taste) spray. Pour Green Enchilada Sauce (10 ounce) over top, using ½ can to 1 whole can, as desired. Bake for about 30 to 40 minutes, or until bubbly and beginning to brown.
Remove from oven and let rest at least 10 minutes before serving. Serve and enjoy!