Preheat the slow cooker if necessary; see the manufacturer's instructions. Heat the oil and butter in a frying pan, add the onion and fry, stirring, for 5 minutes or until just beginning to turn golden.
Stir in the garlic, cook for 2 minutes, then stir in the flour. Gradually mix in the wine and stock and heat, stirring until smooth. Add the sage and season well.
Add the pumpkin to the slow cooker pot, pour over the hot sauce, then press the pumpkin beneath the surface of the liquid. Cover with the lid and cook on low for 6–8 hours or until the pumpkin is tender.
When almost ready to serve, bring a large saucepan of water to the boil, add the gnocchi, bring the water back to the boil and cook for 2–3 minutes or until the gnocchi float to the surface and are piping hot. Tip into a colander to drain.
Stir the cream, then the gnocchi, into the pumpkin, mix together lightly, then spoon into shallow bowls and serve topped with grated Parmesan and a few extra sage leaves, if liked.