Cook the sausage in a cast iron skillet (or other heavy-bottomed skillet) over medium high heat. Once cooked, remove with a slotted spoon and place on a plate lined with paper towels. Reserve the drippings in the skillet.
Drizzle about a tablespoon of olive oil into the skillet with the sausage drippings. Add the onion and both potatoes, cooking over medium high heat. Stir frequently, making sure the potatoes don't stick, and that they pick up any bits of the sausage that were leftover. Continue cooking and stirring until the potatoes are soft and tender. Ours took about 15 minutes, so taste test yours to see when they reach your desired consistency.
Gently crack 5 eggs on top of the mixture. Lightly season with salt and pepper, then back in an oven heated at 350 degrees Fahrenheit for 15 minutes, or until the eggs cook to your desired consistency. At 15 minutes, they should be slightly runny. Give the skillet a good shake to see how much they wobble.
Serve the contents in warm tortillas with fresh avocado and salsa (optional), or simply eat from a plate or bowl.