Heat the oil in a pan, add the leeks, mushrooms and sage and fry for 2 mins until the leeks are starting to soften. It should become quite fragrant. Stir in the rice and cook for 1 min, stirring. Add the wine and stock and bring to the boil. Reduce the heat, cover and simmer for 10-12 mins until the rice is tender.Remove the rice from the heat, then stir in 2 tbsp of the Parmesan and freshly ground pepper. Spoon onto a plate, sprinkle with the remaining Parmesan.