Heat a nonstick pan over medium heat. Once hot, add the oil, onion, and chicken sausage. Saute until the chicken sausage is nicely browned and the onion is soft. Add in the butter.
Add in the eggs, scallions, and cheese. Move the eggs using circular motions with a spatula or wooden spoon to fluff up and cook, (move the pan on and off the heat as needed to prevent the eggs from overcooking or drying out). Remove the pan from the heat while the eggs are still moist. Season with salt and pepper to taste.
Portion the eggs onto the bread and drizzle with hot sauce (if using). Cut in half and serve with apples.