Layer it. Preheat the oven to 400 °F. Then turn on the stovetop medium-low and let the cast iron skillet heat up evenly. Add oil to the hot skillet and pour in one cup of sourdough starter. You will hear a nice sizzling sound. Sprinkle some salt on top of the sourdough starter as needed. Next, break four eggs right on top of the sourdough starter one by one.
Season it. Then, take a knife or fork and scramble eggs on top of the sourdough starter in the skillet. Make sure not to poke inside the dough much. Season eggs with salt and pepper to taste. Use less salt than usual since cheese is a salty ingredient. Sprinkle onion and garlic powder on top of the scrambled eggs.
Cheese and garnish it. Layer thin slices of cheddar cheese on top of the eggs. Sprinkle some sesame seeds on top for garnish.
Bake and serve it. Bake it uncovered until the cheese is bubbly and golden brown. Do not overbake the casserole. It will continue cooking while cooling off on a hot cast iron skillet. Serve with your favorite sides, and enjoy!
