To make the dough, combine the egg, milk, sour cream, oil, and salt in the bowl of a stand mixer fitted with the hook attachment on low speed. Slowly add in flour until the dough pulls away from the sides of the bowl. Turn the speed up to high and mix for 10 minutes.
To make the potato filling, cook the bacon in a large skillet until crispy. Remove 4 slices of bacon from the pan and crumble. Mash the potatoes, salt, 2 tablespoons butter, and cream cheese until creamy. Stir in the 4 slices of crumbled bacon and cheddar cheese.
To make the dumplings, divide the dough in half and cover one half with plastic wrap. Roll out the other half of the dough very thinly and cut out circles with a biscuit cutter or mason jar lid. Add one teaspoon of potato filling into the center of each dough circle and fold in half. Pinch the edges to seal dumplings. Use a fork to further seal the edges. Repeat until all the dough is used. Freeze any extras that you won’t immediately be using.
Boil salted water in a large pot. Add in dumplings, one at a time. Once they float to the top, boil for 4 more minutes. Remove with a slotted spoon.
To make the butter topping, add the remaining 4 tablespoons of butter to the skillet with the cooked bacon and return to heat until warm. Pour butter topping over the dumplings and enjoy!