If you're using fresh pumpkin as opposed to canned pumpkin, start cooking this first. If using canned pumpkin, skip this step. Slice the pumpkin in half carefully using a sharp knife, scoop out the seeds, rub the pumpkin all over with 1 tbsp olive oil and salt, and bake in the oven at 175° for around 45 minutes, until tender. Once cooked, peel off the skin (you might need to allow it to cool a little first!) and cut the pumpkin into chunks. Transfer the pumpkin chunks to a blender or food processor and blitz to form a smooth puree. Around 20 minutes into roasting your pumpkin, heat 1 tbsp olive oil in a non-stick frying pan and fry the sausages over medium heat for 14-16 minutes, turning occasionally, until golden brown and cooked through. Remove from the pan with tongs and transfer to a plate to rest.
As the sausages are cooking, melt the butter in a frying pan and saute the shallots, garlic, sage, carrot and celery for 8-10 minutes, until softened.
Pour in the white wine and allow the sauce to reduce down.
Add the pureed pumpkin and nduja or chilli flakes and blitz the mixture together in a blender until smooth.
Stir through the mascarpone and continue to cook over a low heat for a couple of minutes until melted, stirring continuously.
Slice the cooked Cumberland sausages to around one centimetre-wide and add to the sauce.
Meanwhile, cook the pasta until firm (al dente) and drain, stirring a splash of pasta water into the sauce to bring it all together.
Stir the sauce through the cooked pasta, and garnish with freshly grated Parmigiano Reggiano, sage leaves and freshly ground black pepper to serve.