Prepare the pie dough and press into a 9-inch pie pan. Preheat oven to 425°F.
In a medium-sized pot, whisk together the milk, brown sugar, cocoa powder, corn starch, vanilla extract, and salt until the corn starch is dissolved. Add the vegan butter to the pot.
On medium heat, bring to a simmer, stirring frequently. Remove from the heat as soon as it starts bubbling. At this point, it should be thickened.
Stir in the pecans.
Pour the filling into the pie pan. Use a spatula or spoon to spread the filling out evenly. Trim and crimp the edges of the dough as desired.
Bake for 30 mins. Use a pie crust shield or aluminum foil to prevent the edges of the pie crust from burning.
Remove from the oven and let cool to room temperature before serving. Store in the fridge, tightly wrapped, for up to 3 days.