Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
Beat butter, cream cheese, and both sugars until creamy.
Mix in the egg and vanilla.
Add flour, cornstarch, baking powder, baking soda, and salt. Mix until a soft dough forms.
Fold in chopped pecans and chill the dough for 30 minutes.
Scoop 2 tablespoons of dough per cookie onto the baking sheet. Press pecan halves on top.
Bake for 12–16 minutes, until the edges are lightly golden.
Cool on the baking sheet for 10 minutes before serving.
