Soak porcini mushrooms in 1/4 litre of lukewarm water for about 30 minutes. Wash veal shank slices and dab dry. Rub with salt and pepper and turn in flour. Heat the oil in a roaster.
Brown the meat in it. Peel 2 onions and garlic, dice finely and sauté briefly. Add tomato paste, also briefly sauté. Deglaze gradually with wine and 3/8-1/2 litres of broth.
Cover and stew for 60-70 minutes. In the meantime, peel and finely dice the remaining onion. Heat 20 g fat in a pot and sauté the onion in it. Add rice and fry until transparent.
Add porcini mushrooms with soaking water and 1/2 litre broth. Bring to the boil and let the rice swell at low heat for about 30 minutes. Sort, clean and wash the spinach. Blanch briefly in boiling salted water and drain on a sieve.
Heat the remaining fat and toss the spinach in it, season with salt and pepper. Fold the cheese into the rice. Arrange veal knuckle slices on the spinach. Spread the sauce over it. Garnish with grated lemon.
Add the risotto.