Preheat the oven to 400 degrees F.
Place the whole squash on a parchment lined baking sheet.
Bake for 40 -50 minutes until you can easily run a fork through it.
When the squash is cool enough to handle, peel, de-seed and mash.
Leave the oven on at 350 degrees F.
Grease a 10” x 12” casserole dish.
In a large bowl or on top of a cutting board, combine the squash bagels and 3/4 of the cheese.
Scrape the mixture into the prepared casserole dish.
Heat the butter in a skillet.
When the butter is bubbling, quickly whisk in the flour, thickening the mixture. whisk in the wine and cream. Bring to a boil.
Stir in 3/4 of the gruyere.
Season with nutmeg, salt, and pepper.
When the cheese has melted, pour into the casserole dish.
Place in oven and bake for 30 minutes.
Let cool for 10 minutes before serving.