In a pot, begin to boil potatoes. Cook them until they are soft. Drain. Add the milk, scallions, and HALF of the butter, salt and pepper. Set aside and preheat the oven to 350
In a frying pan, begin to sauté the onions
Add the corned beef and continue to sauté until cooked through and a bit caramelized
Add the sauerkraut and mix everything together.
In a 7 x 11 baking pan, grease, and place the corned beef mixture.
Dollop the mashed potatoes on top and smooth out so they’re even. With a fork, scrape the top of the potatoes lightly.
Place in the oven and bake for 30 minutes or until the top is lightly golden.
Remove from oven and brush over the remaining butter.