Another one of our traditional varieties to remind you of dining in the old country. Cooking InstructionsPierogi are already boiled. If frozen, you can allow them to defrost before heating. This is not necessary, but decreases cooking time. Begin by heating butter or oil in a skillet. Turn down to low-medium heat, adding pierogi to skillet in a single layer. Sauté until heated through and golden brown on each side. Top with sautéed onions in butter and a side of sour cream for dipping. For sweet pierogi, omit the sautéed onions, and add sugar to sour cream, or top with powdered sugar.