Preheat the oven to 400°F or 205°C.
Make the vegan crust according to this recipe. Add the pecans and sugar (if using) to the dry ingredients, prior to adding the vegan butter.
After chilling the dough for 30 minutes, roll it out into a 12-inch diameter circle (about ¼- ⅛ inch thick). Place into the pie pan, gently pressing it to the bottom and sides.
Poke holes in the bottom of the crust. Lay a sheet of parchment paper in the bottom of the crust and fill with pie weights (or dried beans). Bake at 400°F for 6-7 minutes. Remove from the oven, remove the pie weights, and let cool completely before filling.
In a food processor, combine the pumpkin puree, non-dairy milk, cornstarch, maple syrup, brown sugar, vanilla extract, salt and pumpkin pie spice. Pulse until all the ingredients are well combined, and the mixture is smooth.
Transfer the pumpkin pie mixture into the cooled crust, smoothing the top with a spatula. Brush the vegan egg wash on any exposed crust.
Bake covered with aluminum foil for 15 minutes at 400°F (205°C). Reduce the heat to 350°F or 175°C, remove the aluminum foil, and bake for another 25-35 minutes. The pie should look set around the edges.
Let the pie cool completely before serving. The pie will set up completely after cooling for 3 or 4 hours in the fridge. Top with coconut whipped cream or candied pecans.
