Soak the bread roll in cold water for 3-5 minutes until completely soft. Squeeze out the excess water thoroughly. Chop the onion. In a large bowl, mix together the soaked bread roll, minced meat, chopped onion, egg, grated parmesan, soy sauce, salt, pepper, and paprika powder until well combined.
Shape the mixture into roughly 14 meatballs of equal size. Place them on a baking sheet lined with baking paper. Bake in a 180°C (350°F) convection oven for 20-25 minutes until the meatballs are golden brown and reach an internal temperature of 63°C (145°F).