Preheat the oven to 350°F. Line a baking sheet with parchment paper.

Combine melted butter and toasted pecans in a bowl and set aside.

In a large mixing bowl, cream together the butter and brown sugar until fluffy, about 3-4 minutes.

Add vanilla extract and egg; mix until combined.

In a separate bowl, whisk together the flour, baking soda, cornstarch, and salt. Gradually add dry ingredients to wet mixture until just combined.

Stir in the toasted pecans.

Form dough into 2-tablespoon-sized balls and place on prepared baking sheet.

Bake for 12 minutes or until edges are golden. Cool on baking sheet for 3-5 minutes, then transfer to a wire rack to cool completely.