Bring a large saucepan of salted water to the boil and cook the pumpkin until just tender; 8-10 minutes usually. Heat the butter and olive oil together in a large heavy-based saucepan over a medium heat. Sauté the shallots gently for 4-5 minutes then add the garlic and and cooked pumpkin and continue to cook for a further 2 minutes. Add the rice and coat thoroughly in the butter, oil and shallot mixture and cook for 3-4 minutes or until the grains start to turn translucent. Add the white wine and increase the heat to allow it to evaporate almost entirely. Add a ladle of hot vegetable stock to the risotto one at a time, stirring frequently until it is absorbed into the rice. Continue in this fashion until all the stock has been absorbed and the rice is soft yet still defined; usually 30-40 minutes. Adjust the seasoning as necessary. Stir through the Parmesan just before serving. Ladle into serving glasses and garnish with some black pepper before serving.