When the alcohol is completely evaporated, cook the rice with the broth as needed and stir it often. Three quarters of the way add the Castelmagno cubes and stir to make it soften, in the meantime let the onion with the butter and a few leaves of rosemary cook: when the butter is gold, add the coarsely chopped chestnuts and cook high heat for a few minutes. Once the risotto is cooked, proceed to cook stirring until creamy with the remaining butter, then let it stand a few minutes, and cover it with a cotton cloth. Serve the risotto as a ring-shape with a hole in the middle and put a couple of tablespoons of chestnuts. Serve warm, if desired with a light dusting of Castelmagno.