1. Cook bacon in a 9-inch cast-iron skillet over medium heat until crisp, 6-8 minutes. Remove bacon and set it aside on a paper towel-lined cutting board. If needed, scrape brown bits from the pan with a metal spatula. Reserve 1 tablespoon of the drippings and coat the bottom of the pan. Add potatoes to skillet; cook 2 minutes, stirring occasionally. Preheat broiler.

2. Beat eggs in a medium bowl. Stir in milk, salt, and 1 cup of cheese. (You can also add in any small-diced vegetables you like). Add egg mixture to skillet; stir to combine. Cover; simmer until eggs are set on the bottom, 6 to 8 minutes. (Center will be wet.)

3. Uncover; top with reserved half of the bacon, remaining cheese, then the rest of the bacon. Transfer skillet to broiler; broil 5 to 6 inches from heat for 1 to 2 minutes or until eggs are set and cheese is melted. Garnish with chopped green onions.

4. Cut into 6 wedges and serve with sour cream, if desired.