Before you start the crust:
Heat your oven to 375. Cut your squash in half with a good, sharp knife; remove the seeds and rub with olive oil and a sprinkle on a pinch of salt. Place the squash cut side down onto a sheet tray with foil. Roast for about 45 minutes, or until the squash is fork tender.
Start your crust while your squash is roasting:
In a medium bowl, whisk together buckwheat flour, AP flour, brown sugar, and salt. Add the cold cubes of butter, working with your fingertips until the butter is pea-sized and the mixture resembles a coarse and sandy meal. Put the bowl in the fridge and let the flour/butter mixture chill for 15 minutes.
Take the chilled flour/butter out of the fridge and begin to add the ice water a bit at a time, mixing with your fingertips until the dough starts to come together. It should stick together but neither feel wet nor sticky. Form the dough into two "discs", turn the dough onto a sheet of plastic wrap, wrap tightly, and place back in the fridge. At this point, you can keep it in the fridge and use it tomorrow, or next week, or freeze it and use it next month! If you are making the pie in real time, let it rest in the fridge for at least a half hour.
As your squash is cooling, take one of your chilled discs from the fridge, and roll it out to fit your favorite pie dish. The thickness of the crust is up to you, but normally it should be about 1/8 - to no more than 1/4 inch thick. Place it in the dish and stylize the edges of the crust to your liking (I'm a crimper, myself) and let rest in the fridge, about 15 minutes.
Crank your oven up to 425.
Pull out your food processor. Scoop the meat from one of your squash halves and measure about 2 cups of squash. Save the other half for a side dish at dinner, or for lunch. Put the squash into the bowl of your food processor. Add the cream, sugar, maple, salt, and pinch of cinnamon. Puree until there are no lumps. Add butter and flour and puree, once again, until lump-free. Add the eggs, one at a time, until they are incorporated and the filling is smooth. Set aside*.
*Letting the pie filling rest for a few minutes will keep your filling from having a souffle effect if you've worked the eggs too much.
Line your pie crust with foil or parchment and pie weights (I use dried beans). Bake in the 425 degree oven until the sides are golden (about 10 minutes). Turn your oven down to 350. Remove the pie weights from the crust and set them aside (I save my beans right in the foil and use them over and over again). Pierce the bottom of your crust with a fork 5 or 6 times. Put it back in the oven at 350 and bake until the bottom of your pie crust is just starting to crisp, but is still slightly undercooked.
Add the squash filling to the crust, filling to where the egdes begin. You might have some filling left-over (since the size of pie dishes vary). You can bake it in oven-safe jars and serve them as crustless pies! As for your big pie, bake it at 350 for about 20 - 25 minutes, or until the filling is just set (it will have a very slight wobble).
Let the pie cool. Serve it still warm, or at room temperature. It will keep, covered and refridgerated, for up to 3 days.