Chop the onion and parsley finely. Mix in a bowl the ground meat, the chopped onion, the parsley, the oats flakes, the olive oil, the egg, the mustard, the vinegar, the paprika, salt, and pepper. Knead all the ingredients for about 5-6 minutes, using a motion from bottom to top, and occasionally wet your hands with water. Cover the bowl with plastic wrap and place it in the refrigerator for 1 hour. Preheat the oven to 180°C (356°F), with the heating elements on. Lightly oil your hands and shape 12-13 small meatballs, which you then place on a baking sheet lined with parchment paper. Bake for about 30 minutes (depending on your oven). Make the burgers by adding whatever ingredients you like, such as tomato, cheese, onion, mayonnaise, ketchup, etc.