##Mushrooms## Clean, wash if necessary and cut in half. Peel and chop onions. Heat 1-2 tablespoons of oil in a pot. Fry the mushrooms for about 5 minutes, turning them until golden brown. Season with salt and pepper.
Bring 1/2 l water with broth to the boil. Sauté half ##onions## in frying fat. Add rice and fry briefly. Add wine and simmer until all liquid is absorbed.
Add so much hot broth and stock until the rice is covered and keep adding broth as soon as it is absorbed. Simmer for a total of 25-30 minutes.
In the meantime, cut the cheese into 8 cubes for the meatballs. ##Finely dice the tomatoes. Knead minced meat, remaining onions, tomatoes, egg, breadcrumbs and mustard. Season with salt and pepper. Form 8 meatballs from the minced meat mixture, filling each with a cheese cube.
Heat 2 tablespoons of oil in a large frying pan. Fry the meatballs for 5-6 minutes on each side.
Grate parmesan. Wash oregano, shake dry and chop. Stir butter, parmesan, mushrooms and oregano into the rice and heat up briefly. Season to taste with salt and pepper. Serve everything.