Gently mix together warm water, sugar, and yeast. Allow to sit for 10 minutes.
In a large bowl, mix together flour and salt. Form a well in the middle, and pour oil, eggs, and sour cream into it. Mix well, then add the yeasty water.
Mix until everything is well incorporated, then knead lightly for 2 minutes.
Place dough in a large, greased bowl. Cover and allow to rise for 1 hour, or until doubled in size.
As you are waiting for the dough to rise, prepare the filling:
Cook bacon & onions until bacon is almost cooked, but not crispy. Add sauerkraut to the pan, cook and stir well until bacon fat is absorbed and everything is heated through. Season with salt and pepper to taste. Let cool.
Assemble the sauerkraut balls:
Roll dough out to an even 1/4″ thickness. Cut rounds that are between 3″-4″ in diameter.
On the center of each round, place a mound of about 1 Tbsp filling. Gather edges of the round and seal the filling in (like a drawstring bag). Roll around between your hands a bit to get a uniform spherical shape, and place on a lightly greased / sprayed baking sheet. Repeat with the rest of the dough/filling, leaving at least 2″ between dough balls.
Loosely cover cookie sheets with plastic wrap, and allow to rise another hour.
Heat oven to 350F. Remove pastic wrap from cookie sheets, bake for 25 minutes, or until golden. Remove from oven and brush liberally with melted butter.
Great served hot, fresh out of the oven, cold, or even reheated. IF they last that long.
* Note: I like to wear latex gloves for assembly. Spraying hands with pan spray is also a good idea.