Boil the potatoes until they are soft enough to mash. Mash the potatoes and add salt and pepper to taste. Mix in the cooked bacon and the bacon grease left over from cooking along with the Sauerkraut and 2 table spoons of butter. You may add milk into the potatoes if you'd like. Cut the Kielbasa into large pieces and warm in a pan on the stove until brown.
Note: When cooking the bacon remove it from the heat or oven before the bacon becomes crispy.