Homemade Pittsburgh Pierogies

INGREDIENTS

• 2 cups flour, plus extra for kneading and rolling dough
• ½ teaspoon salt
• 1 large egg
• ½ cup sour cream
• ¼ cup butter, softened and cut into small pieces
• Butter and onions for sauteing
• :
• 1 lb red potatoes
• ¼ of a large onion, finely chopped
• 2 oz. cheddar cheese, finely grated
• Salt & pepper