1) To make the crust: Lightly grease a 9" pie pan.
2) Whisk together the flour or flour blend, sugar, ClearJel, xanthan gum, and salt.
3) Cut the cold butter into pats, then work the pats into the flour mixture until it's crumbly, with some larger, pea-sized chunks of butter remaining.
4) Whisk the egg and vinegar or lemon juice together until very foamy. Mix into the dry ingredients. Stir until the mixture holds together, adding 1 to 3 additional tablespoons cold water if necessary.
5) Shape into a ball and chill for an hour, or up to overnight.
6) Allow the dough to rest at room temperature for 10 to 15 minutes before rolling.
7) Roll the crust on a piece of plastic wrap, on a silicone rolling mat, or in a pie bag that's been heavily sprinkled with gluten-free flour or flour blend. Invert the crust into the prepared pie pan.
8) To make the filling: Mix the flour, spices, and salt in a medium-sized mixing bowl.
9) Add the sugar and pumpkin, blending thoroughly.
10) Stir in the syrup and milk. Allow the mixture to rest for 30 to 60 minutes at room temperature; or up to overnight in the refrigerator, if desired; this allows the flavors to meld, and will make the filling smoother.
11) Add the beaten eggs, whisking until combined.
12) Pour the filling into the prepared crust. Cover the edge of the crust with a crust shield, or aluminum foil.
13) Preheat the oven to 425°F.
14) Place the pie on the middle rack of your oven, and bake it for 20 minutes.
15) Reduce the oven temperature to 350°F, and bake for an additional 30 to 35 minutes, or until the temperature at the center is at least 175°F, and a knife inserted 1" from the edge comes out moist, but clean.
16) Remove the pie from the oven, and cool to room temperature (or chill) before serving. Serve with whipped cream, if desired.
Yield: one 9" pie, about 8 to 12 servings.