Heat the oil in a saucepan and sauté the onion and ham cubes in it. Add the rice and fry until translucent. Deglaze with white wine and some of the chicken stock. Finish cooking the rice in about 20 minutes, gradually adding the remaining chicken broth while stirring. Fold the peas into the rice about 5 minutes before the end of the cooking time and cook at the same time. Season everything with salt and pepper.
Stir two thirds of the parmesan and butter into the risi bisi. Let it steep for about 5 minutes and then serve sprinkled with the rest of the parmesan.