Work in the sour cream and soft butter with a dough blender until the dough comes together in a slightly rough, sticky ball.

Using your hands, knead and fold the dough until the dough becomes less sticky but still quite moist.

Wrap the dough well in plastic wrap and refrigerate for 30 minutes, or up to 48 hours.

Bring a large pot of heavily salted water to a boil over high.

Place 1 1/2 - 2 teaspoons of filling on each circle of dough. Gently fold the dough over, forming a pocket around the filling. Pinch the center edge of the dough together and work your way down on both sides, pinching the dough over the filling and pushing in the filling as needed, making sure the potato mixture does not break the seal. If needed use dap some water to help seal edges. At this point the pierogies can be frozen up to 4 weeks or refrigerated overnight.

Heat 12 inch skillet over medium heat and add 2 tablespoons of butter.

To cook the pierogi, add a single layer of pierogi to the pot of boiling water. No more than 10 at a time to prevent sticking. Cook until they rise to the surface, about 2 minutes, then cook another 2 to 3 minutes until puffy. Frozen pierogies may need an additional couple of minutes. Use a slotted spoon to drain and transfer into buttered pan.

Add boiled pierogi in a single layer to pan and avoid overcrowding. Cook until crisp and golden, 1 to 2 minutes per side. Repeat with remaining pierogi, adding more butter as needed.