How to Make It
Preheat the oven to 400°. Cut the butternut squash in half and scoop out the seeds. Brush both halves with olive oil then place cut side down on a baking pan. Roast for 40 minutes, or until tender. Set aside to cool.
Make the pierogi dough: In a bowl, mix together the flour, sour cream, egg, olive oil, and salt until the ingredients bind together. Place the dough on a lightly floured surface and knead for a couple minutes, or until smooth. Wrap in plastic wrap and let rest for 30 minutes.
Scoop out the butternut squash flesh and mash. Stir in the sage leaves and season with salt and pepper.
On a lightly floured surface, roll out the dough to about 1/8-inch thick. Using a 3-inch round cutter, cut out 12-15 rounds. Brush the edges of each round lightly with water, then place 1 tablespoon of filling on one side of the rounds. Fold the dough over, making half moon shapes, pressing out the air. Press and crimp the edges to seal the pierogi.
Bring a large pot of salted water to a rolling boil. Cook the pierogi for 3-5 minutes, or until tender. Drain.
Heat the butter in a large skillet over medium heat. Add the pierogi to the skillet with the butter and sear each side for about 1 minute or until golden.