In a large bowl, mix the mashed potatoes and horseradish.

Stir in the dried grated potato, salt, pepper, flour, and baking powder.

In a medium bowl whisk together the eggs and milk.

Stir the egg and milk mixture into the potatoes until the mixture is creamy and has the consistency of thick pancake batter. *Note - if the mixture is too thick, add a splash of milk.

Add approximately 1 tablespoon of oil to a large skillet over medium/high heat.

Spoon enough potato mixture into the skillet to form a pancake that is approximately 6" round and ¼" thick. *Note - use the back of a spoon to help achieve this size.

Cook the pancake until golden brown on the first side and then carefully flip and cook the second side until golden.

Place corned beef and Swiss cheese on half of the potato pancake and flip the plain half of the pancake over the filled half of pancake.

Cover the pan loosely and allow the cheese to melt.

Remove the completed boxty to a baking sheet and keep warm in a low oven while preparing the remaining boxty.