Sweat the leek in the olive oil, fry the pizza spice, bell peppers and carrots, season with salt and pepper. Mash the kidney beans and mix with the egg, cheese, tomato paste and breadcrumbs. Stir in the vegetables and form small meatballs and place on a baking sheet lined with baking paper.
Bake for 20 minutes, turn after 10 minutes if necessary.