Cut the squash in half, scrape out the seeds and place the squash cut-side down on a baking sheet. Roast for 50 to 55 minutes. Halfway through the cook time, flip the squash so it is cut-side up to release some steam and dry the squash out a bit. Once you can press the squash with your finger and make an indentation, the squash is cooked. Set aside until cool enough to handle, then scoop out the flesh.
In a small saucepan over medium-low heat, the combine maple syrup, butter and 1 cup of the roasted squash. Paddle until smooth with a rubber spatula. Add the cream cheese and salt and mix until smooth. Cover and keep warm over low heat.
Toast the bread until golden on both sides, then rub the bread with the ginger. Set aside.
Thread the marshmallows onto skewers and toast over a fire (either in a fireplace or over a gas range flame) until darkly toasted and melty but not burnt.
To assemble: Smear each slice of bread with some warm squash puree. Top with some chocolate shavings, then with a marshmallow. Consume immediately, in front of the fire.