Heat sausage in a large skillet over medium heat for 2-3 minutes. Add the egg and season with salt and pepper to taste. Add a splash of milk. Stir egg/sausage until set. Turn off heat.
To assemble your tostada stacks, place four tortillas on a large cookie sheet. top each with a spoonful of the egg mixture and top with cheese. Place another tostada on top and top with more egg and then cheese. Top with one more tostada. Top the last tortilla with more cheese.
Place in oven for 5-10 minutes or until cheese is fully melted.
While tostadas cook, blend your sour cream and avocado in a blender. Set aside.
Top cooked tostadas with pico, avocado chunks, and green onion. Finally, top with the avocado cream mixture.
Note: You can make them in stacks of two instead of three if you'd like a less filling breakfast. It would still be big enough!