Preheat your oven to 400° and line a baking sheet with parchment paper.
Prep the squash by cutting it carefully in half and scooping out all the seeds and pulp with a spoon.
Roast the squash face down on the baking sheet with a small splash of water in the pan, baking for 35 to 45 minutes until the flesh is completely tender and easily pierced with a fork.
Scoop the flesh out of the skin and into a mixing bowl, discarding the shell.
Mash and whip the warm squash using a hand mixer or potato masher, blending in the melted butter, roasted garlic, and heavy cream until fluffy and smooth.