Prepare the vegetable stock with the stock cube. Melt the butter in a pan, then add the onion and let it brown. Add the rice and let it toast for a few minutes, then add the champagne and let it fade for a few minutes on high heat. Add a few ladles of broth to cover the rice. Stir the rice from time to time, adding the broth that has evaporated during cooking, so that the rice never remains uncovered. When the rice is cooked, stir in the diced Provolone Fattorie Cremona and grated Grana Padano Fattorie Cremona.