Pierogi (Polish Dumplings)

INGREDIENTS

• Sauerkraut Filling:
• 2 tablespoons butter
• 1/3 cup chopped onion
• 1 1/2 cups sauerkraut, drained and minced
• salt and pepper to taste
•  
• Potato Filling:
• 3 tablespoons butter
• 1/2 cup chopped onion
• 2 cups cold mashed potatoes
• 1 teaspoon salt
• 1 teaspoon white pepper
• Dough:
• 3 egg
• 1 (8 ounce) container sour cream
• 3 cups all-purpose flour
• 1/4 teaspoon salt
• 1 tablespoon baking powder