Preheat oven to 350 degrees. Cook bacon until crisp, drain and crumble reserving 2 tablespoons bacon drippings. Save bacon for topping later.

Add reserved bacon drippings, milk, and butter in a medium saucepan and bring to a boil over medium heat. Gradually whisk in grits, 1 teaspoon salt, and 1/2 teaspoon pepper. Cook and whisk constantly until very thick, about 15 minutes. Remove from heat and let stand 10 minutes. Stir in 1 cup cheese and let stand another 10 minutes.

Stir in 1 egg and spread in a 9-inch springform pan coated with cooking spray.

Bake at 350 degrees for 25 minutes or until set and browned. Sprinkle remaining 1 1/2 cups cheese over warm grits, spreading to edges. Let stand 15 minutes. (Continue cooking or cool and refrigerate overnight after this step.)

Reduce oven temperature to 325 degrees (or preheat oven to 325 degrees in the morning). Combine half-and-half, cream, onions, and remaining 5 eggs, 1/2 teaspoon salt, and 1/2 teaspoon pepper. Pour over grits and sprinkle with crumbled bacon. Place pan on a foil-lined baking sheet.

Bake for 1 hour and 15 minutes or until lightly browned and just set. Let quiche stand 20 minutes. Run a sharp knife around edges of quiche, then remove sides of pan. Serve immediately.