Heat the oven to 400. Cut a butternut squash in half lengthwise and place face down on a lightly buttered or oiled baking sheet.
Bake the squash until the cut edges are browned and bubbling. Remove from the oven and allow to cool. Remove the seeds and pulp and discard. Scoop the flesh out of the skin.
Mash 1/2 C. of the squash, or puree with a food processor. Reserve the rest of the squash for another use.
Add the pureed squash to a saucepan with 1 C. heavy cream, 3/4 C. whole milk, and 1/4 C. maple syrup. Stir with a whisk and taste; add more maple syrup if needed. Heat to a simmer.
In a medium bowl, combine 6 egg yolks, beaten, with 1/4 t. ginger powder (or 1 t. minced fresh ginger), 1/8 t. nutmeg, and 1/4 t. salt.
Pour the squash mixture into the bowl with the eggs, whisking constantly. Butter or oil 6 individual ramekins, then pour the custard into them
Boil a teakettle full of water. Preheat the oven to 325. Arrange the ramekins inside a baking pan with sides that are at least as tall as the ramekins. Pull out out the middle rack in the oven so you can set the baking pan on it, then fill the pan up with water carefully so it does not get into the ramekins.
Bake for 40-45 minutes, or until they are set and a knife inserted in the custard comes out clean.
For the persimmons: Cut off the “hat” at the stem end of 2 Fuyu Persimmons, then cut the fruit into 1 inch cubes and arrange in a single layer on a baking sheet. Melt 1 T. butter and pour it over the fruit, then toss to combine. Roast at 350 until they are soft, about 20 minutes. Then turn the oven to broil and brown them for a few minutes, until the outsides are crisp — taking care not to let them burn.
Serve the custards with a spoonful of persimmons on top of each one.