Dice the pumpkin, put it in a saucepan full of water and cook for 10 to 15 minutes. When soft mix it with a blender and keep warm. Meanwhile, brown a chopped onion in a large frying pan with a drizzle of oil, add the rice and toast it. Add the pumpkin broth and bring it to the boil. Meanwhile, mix the cream with the gorgonzola in a small saucepan until well mixed. Cream the risotto with butter and cheese, plate it and pour the gorgonzola cream on top. Top with hazelnuts that you have previously toasted.