Prep: Slice the avocado in half, remove the pit and scoop the flesh into a small bowl. Use the back of a fork to mash the avocado until it's smooth and spreadable. Add a little salt and pepper and mix to incorporate.
Cook: Heat the butter in a small trying pan over medium-high heat until it bubbles and then crack an egg in and cook to your liking, flipping once if you're making a fried egg or mixing it around the pan for a scrambled egg.
Toast: While the egg is cooking, toast the bread until crispy and golden.
Assemble: Using a spoon, spread the avocado evenly on the toast, top with your egg and season with a little more salt and pepper.