Preheat your oven to 350 degrees. Spray a 9 by 13 inch casserole dish with cooking spray.
In a large skillet, cook the breakfast sausage, breaking it up. Cook just until it is begins to brown.
Add the onion, bell pepper, and garlic to the meat. Cook, stirring occasionally, until the onions are translucent, about five to seven minutes.
While the vegetalbes are cooking, whisk the eggs. To the eggs, add milk, heavy cream, green chiles, salsa and salt. Then stir in 1 1/2 cup cheese, and the bread. Mix to combine.
When the vegetable and meat mixture is ready, drain the excess grease from the pan, and add it to the egg mixture. Pour everything into the prepared pan and top with 1 cup cheese.
If you used dry bread, you can bake it right away, if you used fresh, let the casserole soak overnight. Read more about this here. Bake for 60 minutes and 15 minutes uncovered, or until the eggs are set - when the casserole starts to pull away from the side of the casserole dish and you can stick a knife in the middle of the dish and not see excess moisture. (Please note that if you started with dry bread and didn't need to refrigerate the casserole overnight, you will only need to bake it for 50 minutes before uncovering it and baking it for the final 15 minutes.)
Let the casserole sit for 10 minutes before cutting into it.