Heat oven to 350°F. Line two baking sheets with parchment paper.
Beat butter and 1/2 cup powdered sugar until light and creamy, about 2 minutes.
Mix in vanilla and salt until combined.
Add flour and cornstarch. Mix on low just until a soft dough forms.
Fold in mini chocolate chips. Chill dough 10 minutes if sticky.
Scoop dough into 1-tablespoon portions and roll into balls. Arrange 2 inches apart on sheets.
Bake 11–13 minutes, until tops are set and bottoms are lightly golden.
Cool 5 minutes. Roll warm cookies in powdered sugar. Cool fully, then roll again for a thicker coat.