Melt 1 tablespoon butter in a large cast iron skillet over medium heat. Add diced onions and cook until they begin to soften, about 3-4 minutes.

Add diced potatoes to the skillet, stir to combine with onions. Cover the skillet and cook for 10-12 minutes, stirring occasionally, until potatoes begin to soften and develop some color.

Add the remaining tablespoon of butter to the skillet. Increase heat to medium-high and continue cooking the potatoes uncovered, stirring occasionally, until they become crispy and golden brown, about 8-10 minutes.

Add the chopped corned beef, beef broth, Worcestershire sauce, thyme, pepper, and salt to the skillet. Stir to combine all ingredients.

Press the mixture down with a spatula and cook undisturbed for 4-5 minutes until a crust forms on the bottom.

Gently flip portions of the hash, allowing new areas to crisp up for another 4-5 minutes.

If desired, create 4 small wells in the hash and crack an egg into each well. Cover the skillet and cook until eggs reach desired doneness, about 3-4 minutes for runny yolks.

Garnish with fresh parsley before serving hot.