In a large skillet, cook the necessary mix-ins such as bacon, sausage, or vegetables, until browned and tender. Drain any excess grease, and set aside.
Preheat the oven to 350 °F and grease a 10 inch quiche pan with cooking spray.
Whisk together the eggs, milk, salt, pepper, red pepper flakes, and garlic until combined completely.
Mix in the shredded hash browns, cheeses, ham, spinach, broccoli, and sauteed onions. Stir until all ingredients are evenly incorporated.
Pour the egg mixture into the prepared quiche pan and bake uncovered for 45 minutes.
If the sides of your quiche pan are shallow and you don’t think you can carry a full pan from the counter to the stove, place the pan in the stove and then fill it. This way it doesn’t spill. You can fill the quiche pan to the brim.
After baking, let the quiche sit and cool for about 10 minutes before serving. It will have risen in the baking process and letting it sit and cool will allow it to settle back into the pan to an even level.