In a large, heavy-bottomed pan, heat the oil with 25g butter. Add the onion and a pinch of salt and cook on a low heat for 10 mins or until soft. Add 60g bacon and cook for a further 5 mins until the bacon releases its fat. Then increase the heat to medium, add the pumpkin and stock and season. Bring to the boil, then reduce the heat to a simmer, cover with a lid and cook for about 40 mins until the pumpkin is soft. Pour in the cream, bring to the boil again and remove from the heat. Set aside some of the liquid, then blend the remaining pumpkin until smooth and velvety, adding liquid back into the pan bit by bit as you go (add more liquid if you like it thinner). Strain through a fine sieve, check the seasoning and set aside.