Peel and finely dice the onion and garlic. Heat butter in a pot. Fry onion and garlic over low heat until translucent. Add rice and sauté briefly. Add broth and wine bit by bit, stirring from time to time.
Always add the next portion of liquid only after the rice has absorbed the liquid. Cook for a total of 30-35 minutes. Grate the parmesan. Halve the chestnuts, fold them into the risotto 5-7 minutes before the end of the cooking time and simmer.
Wash the sage, shake dry, remove leaves except for something to garnish, pluck from the stems and cut into fine strips. Mix 75 g parmesan and sage into the risotto. Season to taste with salt, pepper and a little sugar.
Serve the risotto, garnish with sage and sprinkle some Parmesan cheese on each.