Preheat the oven to 300 degrees F. Line 2 baking sheets with parchment paper and set aside.
In a stand-up mixer, using the paddle attachment, cream vegan butter, sugar, and vanilla until light and fluffy, scraping down the sides as needed. Add the flour and mix until combined.
Mix in the finely chopped pecans. You may need to finish folding the nuts in by hand as some of them get stuck in the bottom of the bowl.
Roll dough in balls about 1 heaping tbsp big. Place on the baking sheet and bake for 25-30 minutes. Check for doneness by cutting one in half to ensure that it's cooked all the way through. Transfer cookies onto a wire cooling rack and allow to cool completely.
Place powdered sugar in a large ziplock bag with about 6 cookies at a time. Shake it around until cookies are completely coated. Repeat until all cookies are coated. Alternatively, you can place the powdered sugar in a shallow bowl and roll the cookies to coat.
Serve or store in an airtight container for up to 5 days. Cookies can be stored in the freezer for up to 2 months.
Let cookies cool completely before coating them in powdered sugar. If the cookies are still warm, the sugar will melt.
Store the cookies in an airtight container at room temperature for up to 5 days or in the freezer for up to 2 months.