This pie tastes like the perfect blend of pecan pie and pumpkin pie -- only it's neither one and even better!
For this recipe, the butternut squash can be roasted two days ahead of time -- and should be roasted at least 6 hours ahead. Here's How to Roast a Butternut Squash. (It is not included in the prep time for this recipe. You can also purchase butternut squash purée.
Add the pecans and walnuts to a food processor fitted with the blade attachment and blend until it's just becoming -- but isn't quite -- a paste. They should be somewhere between a powder and paste.
It will be about 1/2-inch thick, thicker than a typical pie crust. Be sure to bring the crust on top of the top edge as it will shrink a bit during the baking time.
Place the prepared crust in the refrigerator for at least 45 minutes, and during that time, preheat the oven to 350°F.
Once the crust is about room temperature, pour in the filling. Keeping the filled pie on the baking sheet, place it in the (still) preheated 350°F oven and very loosely, cover it with a piece of foil. (The foil should not be wrapped around the pie plate, it should be sitting on top, more or less.) Bake it this way for 1 hour, then remove the foil and bake until it's set, about 10 more minutes. When you move the baking sheet, it should no longer jiggle in the center. You can also stick a wooden skewer int he center -- it should come out clean when it's done. (Cooking times may vary.)
If your squash purée isn't smooth, you can blend it in a food processor with the blade attachment for about 30 seconds.
To save time, you can buy butternut squash purée.
If you don't have, or can't get potato starch, you can use corn starch. Mix 1 tablespoon with 1 tablespoon of water, before adding it to the filling.