Preheat the oven to 375 degrees.
In a large cast iron pan, brown breakfast sausage. When it’s cooked, drain well, and lay on a paper towel to absorb residual grease.
Whisk eggs, salt, pepper, milk and cheese in a large mixing bowl.
Now, you’re going to layer all the ingredients kind of like a lasagna. First, grease a 9×13 baking dish or 12 inch diameter cast iron with butter. Spread shredded potatoes on the bottom, add sausage on top. Sprinkle green chilies and onions over that. Slowly pour the egg and cheese mixture over everything and top with the reserved 1/2 cup of shredded cheese.
Bake for 35-45 minutes or until the middle is set and cooked through.
Serve as is or drizzle with hot sauce, my favorite is Tapatio or Texas Pete’s! You can even get creative and mash up your breakfast casserole slice and roll it in a tortilla! Enjoy!