Slice English muffins in half horizontally and toast until golden. Remove from toaster and spread butter onto the open faces of each half. Meanwhile, place a 12-inch skillet over medium-high heat and add 2 tablespoons of butter. Once butter is melted and shimmering, swirl to coat the pan, then gently crack four evenly-spaced eggs into the pan. Sprinkle each egg with salt and pepper, add one tablespoon of water to the skillet, reduce heat to medium, and place a lid on top. Cook, covered, for about 4 minutes or until the egg yolks are still a bit runny but starting to appear slightly opaque. Meanwhile, slice the avocado and lay several slices onto the lower half of each muffin. Using a spatula, gently transfer each egg to the bottom half of each English muffin. Gently place the top half of the English muffin onto the bottom half and serve.