Cook the breakfast pork sausage in a large cast iron skillet until browned. Transfer the sausage out of the skillet and remove any excess grease.

Melt the butter in the same cast iron skillet over medium-low heat. Stir in the flour and cook for 2-3 minutes until thickened.

Gradually whisk in the milk, adding about 1/2 cup at a time, until a smooth gravy forms. Add the salt, green chiles, and cooked sausage back into the skillet and stir to combine.

Whisk the eggs with the milk and salt in a separate bowl.

Preheat the oven to 350°F (177°C). Spread half of the biscuit cubes across the bottom of a greased 9×13 pan. Pour the egg mixture over the biscuits, then add the cheese and some of the gravy while reserving some gravy for serving. Add the remaining biscuit cubes on top.

Bake for 35 minutes, until the eggs are set.

Serve warm slices with the reserved green chile sausage gravy spooned over the top. Thin the gravy with a little more milk if needed to reach a pourable consistency.