Preheat oven to 400F.
Cut squash in half through the stem and place cut side down on lightly greased baking dish. Bake until easily pierced with a knife, about 45-60 minutes.
Using a spoon, scoop out the seeds and heavy fibers, discard or save the seeds for other use.
In a small sauce pan, combine butter and milk and heat gently over medium heat until hot. About 1 minute. Remove from heat.
Using a potato masher, mash the squash until smooth. Add int the milk mixture and ginger. Combine. Season with salt and pepper to taste. Serve immediately.