Preheat oven to 325°F. Line two baking sheets with parchment.
Toast pecans in a dry skillet over medium heat until fragrant, 5–7 minutes. Cool, then chop.
Beat butter and powdered sugar on medium speed until light and creamy, about 2 minutes.
Mix in vanilla and salt until combined.
Whisk flour and cornstarch in a bowl. Add to the mixer in two additions.
Blend on low just until a soft dough forms. Do not overmix.
Fold in chopped pecans with a spatula.
Chill the dough for 20 minutes to firm up for easier shaping.
Scoop tablespoon portions, roll into balls, and space 2 inches apart on sheets. Flatten to 1/2 inch thick.
Sprinkle lightly with coarse sugar, if using.
Bake 16–18 minutes until set with pale golden edges, rotating pans halfway.
Cool on the sheet 5 minutes, then transfer to a rack to cool completely.