Something really special happens when the salty corned beef forms a crispy layer then marries with the buttery onion and potatoes. It's that same something found in most rustic dishes, that are so full of character and flavor.
In a large cast-iron skillet over medium heat, melt 2 Tbl. of butter. Add onion, sauté until translucent. Increase heat to medium-high, then add the cubed corned beef and potatoes, pressing mixture into skillet. Allow to cook undisturbed for 7-10 minutes, until bottom begins to brown.
Turn hash over in sections, adding additional butter if needed, then press into the skillet. Cook second side 5-7 minutes until nicely browned.
Meanwhile prepare poached eggs.
Serve hash topped with poached eggs, chopped fresh parsley, and cracked black pepper.