Heat the butter and olive oil in a large cast-iron skillet over medium heat until the butter is fully melted and bubbling.

Add the diced potatoes to the skillet, spreading them into an even layer. Let them cook undisturbed for 4 to 5 minutes until the bottoms start to turn golden brown.

Pour the beef broth into the skillet and immediately cover it with a tight-fitting lid. Let the potatoes steam for about 5 minutes, or until they are easily pierced with a fork.

Remove the lid and stir in the chopped onion, garlic powder, and black pepper. Cook for another 3 to 4 minutes, stirring occasionally, until the onions are soft, fragrant, and translucent.

Fold the diced corned beef into the potato and onion mixture. Press the hash down gently with a spatula into a flat, even layer to maximize contact with the hot pan.

Cook the hash undisturbed for 4 to 5 minutes to develop a dark, crispy crust on the bottom. Flip the hash in large sections using a spatula, and cook for an additional 3 to 4 minutes until crispy all over.

Remove the skillet from the heat and garnish the hash with freshly chopped parsley. Serve immediately, ideally topped with a runny fried or poached egg and a dash of your favorite hot sauce.