Wash and dry all produce. Preheat oven or toaster oven to 400 degrees. Thinly slice half the chorizo into rounds. Dice other half. Cut potatoes into 1/2-inch cubes. Halve, peel, and finely dice onion. Halve and pit avocado. Scoop out flesh from peel with a spoon, then thinly slice.

Add chorizo rounds to a large pan over medium heat. Cook, tossing occasionally, until oil has rendered and rounds are crispy, 4-5 minutes. Remove from pan with slotted spoon and set aside.

Increase heat under pan to medium-high. Add potatoes and diced chorizo, tossing to coat. Cook until potatoes are crisped, about 15 minutes. (TIP: If pan is dry, add a drizzle of oil.) Add onion and cook until softened, 3-5 minutes. Season with salt and pepper. Remove mixture from pan and set aside, covering with foil to keep warm.

Split buns in half and place on a baking sheet cut-side up. Place a handful of cheddar cheese on each of the bun tops. Toast in oven until cheese is melted and buns are golden brown, 2-4 minutes

Carefully wipe out pan with a paper towel, then heat a drizzle of oil in it over medium-high heat. Crack eggs into a small bowl, checking for any bits of shell. Gently slide into pan. Cook eggs sunny side up to desired doneness, 2-4 minutes.

Layer chorizo and avocado slices on bun bottoms, then top each with an egg and bun top to make sandwiches. Serve with hash and any remaining avocado or chorizo on the side.