Step 1: In a skillet, sauté the diced onion and garlic over medium heat until softened. Add the ground meat, salt, pepper, and marjoram. Cook until the meat is browned and cooked through. Drain excess fat and let the mixture cool.
Step 2: In a large bowl, combine the cold mashed potatoes, egg, and flour. Mix until a soft dough forms. Add a little more flour if the mixture is too sticky to handle.
Step 3: Flour your hands and divide the potato dough into 8 equal portions. Take one portion and flatten it into a circle in your palm.
Step 4: Place 1-2 tablespoons of the meat filling in the center of the potato circle. Carefully fold the edges over the meat and pinch to seal, forming a thick pancake patty.
Step 5: Heat about 1/4 inch of oil in a large skillet over medium heat. Fry the pancakes for 4-5 minutes per side until they are golden brown and crispy. Serve hot with sour cream.