Pour the Noël or winter brew into a medium-size saucepan, leaving behind any yeast sediment. Place over medium heat, and add the ginger and salt. Bring the beer almost to a boil, then remove from heat and let it rest to infuse the ginger. Using a large spoon, scrape out the squash flesh, leaving behind the skin, and pulse in a food processor until the mixture is smooth, adding in the warmed brew a little at a time. Add in the salt, nutmeg and butter, and purée until smooth and creamy. Transfer the purée to a pre-warmed serving bowl and place on the table.