Place the diced potatoes in a pot of water and cook until just fork tender. Drain thoroughly and set aside so excess moisture evaporates.

Heat part of the butter in a large skillet over medium heat. Add the cooked potatoes and diced onion along with salt and pepper, cooking while stirring occasionally until the onions soften and the potatoes begin to develop golden edges.

Add the chopped corned beef along with the garlic powder and onion powder, stirring gently to distribute everything evenly throughout the pan.

Use the back of a spatula to press the mixture into a flat, compact layer. Let it cook undisturbed until a crisp crust forms on the bottom.

Scrape and turn sections of the hash so the browned portions come to the top, then add the remaining butter and mix lightly.

Press the mixture down again into an even layer and continue cooking until another golden crust develops. Repeat pressing and browning until the desired level of crispiness is achieved, then serve hot.