Pierce the sweet potatoes in a few places with a fork, and roast on a rimmed baking sheet at 450 F. Roast until the sweet potatoes are very soft when you push on them with a spoon, and the sugars are bubbling out and caramelizing on the baking sheet. Depending on the size of your sweet potatoes, this could take anywhere from 30 minutes to 11/2 hours, so just test them every 20 minutes while they are roasting.
Once they are cool enough to handle, scoop the flesh out of the skins. Combine the scooped out sweet potatoes with butter, maple syrup, cinnamon and heavy cream in a food processor or stand mixer. Quantities are up to you depending on your taste. I recommend starting with a little of each ingredient and adding more as you blend and taste. Whip the potatoes until they are smooth and fluffy.