How to Make It
Put the potatoes in a large pot and cover with water. Add a large pinch of salt and bring to boil. Cook over moderately high heat until tender, about 20 minutes. Drain the potatoes and return them to the pot. Shake the pot over the heat for 10 seconds to dry the potatoes. Remove from the heat. Add the butter and cream and coarsely mash the potatoes. Season lightly with salt and generously with pepper.
In a food processor, pulse the corned beef until coarsely shredded. Stir the corned beef into the potatoes.
In a large nonstick skillet, heat 1 tablespoon of the oil. Add the onion and season lightly with salt. Cover and cook over moderate heat until softened, about 5 minutes. Stir the onion into the hash. Wipe out the skillet.
Preheat the oven to 325°. In the same skillet, heat 1 1/2 tablespoons of the oil until shimmering. Add half of the hash mixture and flatten with a spatula. Cook over high heat for 2 minutes. Reduce the heat to moderately high and cook until the hash is richly browned on the bottom, about 2 minutes longer. Working in sections, turn the hash over and cook until browned on the other side, about 2 minutes. Transfer the hash to a large rimmed baking sheet and keep warm in the oven. Repeat with the remaining 1 1/2 tablespoons of oil and hash. Serve with fried eggs, hot sauce and ketchup.