1 serrano pepper (seeded if desired), diced
2 tablespoons butter
1 (16-ounce) can refried beans
1 avocado, pitted, peeled and diced,
3/4 cup cheddar cheese, shredded
In a large skillet over medium-high heat, cook and crumble the sausage until browned. Drain and add cooked meat back into the pan. Stir in the onion and serrano pepper. Cook for 3 to 4 minutes. Add the garlic and cook 1 to 2 minutes more. Set sausage mixture aside and keep warm.
Add butter to skillet and melt. Working in batches, crack the eggs into the pan. Cook until the bottoms are set and the edges golden, 1 to 2 minutes. Turn the heat to medium-low, cover, and cook until set, about 1 minute more.
Heat the refried beans. Spread the beans on the tostados. Top beans with cheese, prepared sausage mixture, avocado slices and then egg. Serve warm.