Pre heat the oven to 400F / 200c.
Cut the butternut squash in half lengthways and scoop out the seeds with a spoon.
Lay the squash on a baking sheet, brush with oil and sprinkle with a little salt and pepper.
Roast in the hot oven til fork tender, about 45 minutes.
Take the squash out of the oven and let cool slightly so that it's easy to handle.
Heat the butter and cream in a pot on the stovetop. Just warm it so that the butter melts, don't boil it.
Scoop out the flesh of the butternut squash into the cream and butter, and discard the skin.
Add the cinnamon, salt and black pepper to the squash and mash together til smooth.