Place pumpkin on a tray in the oven to roast, 190c/375f.
Meanwhile, using a large saucepan and some olive oil, fry the onion until soft. Add the rice and stir. Cook for 2-3 minutes stirring constantly.
Add the wine and vinegar, stirring until the liquid has been absorbed.
Pour in 1 cup of stock and stir until absorbed. Add the garlic, pepper, zucchini and mushrooms.
Now, add the stock 1 cup at a time, waiting until each cup has been absorbed until adding the next.
By the time the last of the stock has been absorbed, the pumpkin should be cooked.
Add the pumpkin and parsley to the risotto, stir to combine.
When the grains are plump and soft, and the liquid is absorbed the risotto is ready! Season to taste, and sprinkle parmesan over the top.