Fry half the onion in 1 tablespoon of the oil in a large saucepan. Add the rice and toast it, stirring, for 5-7 minutes. Add the wine and simmer, until evaporated.
Bring the stock to the boil. Add enough of the stock to just cover the rice. Season.
In another pan, fry the other half of the onion and the pancetta in the remaining oil for 5 minutes. Add the pumpkin and cook for 10 minutes more.
Keep adding the stock to the risotto, stirring continuously. After 15 minutes, add the pumpkin and pancetta.
Test the consistency of the rice. When the rice is cooked, add the parmigiano-reggiano, butter, and parsley, and whisk vigorously until it is soft and smooth.