In a 4-inch cast-iron or heavy-duty skillet, heat 1/2 cup of the olive oil until very hot but not smoking. Crack an egg (or 2 eggs) and add to the hot oil. Sprinkle with fleur de sel and cook for about 1 minute, until the whites are bubbly and the outer edges become brown and crisp. Just before the eggs are done, spoon a little of the oil onto the yolks to create an opaque film over them. Remove the eggs and place over the asparagus. Spoon about a tablespoon of brown butter over the asparagus and egg, arrange the guanciale or pancetta on either side and sprinkle with grated Parmesan cheese.