In a large mixing bowl, cream together melted butter with granulated sugar and brown sugar until light and fluffy, about 3-5 minutes.

Add the egg and vanilla extract, mixing until completely smooth and well combined.

Gradually mix in flour, cornstarch, baking powder, baking soda, and cinnamon until just combined.

Gently fold in chopped pecans and toffee bits.

Cover the dough with plastic wrap and chill in the refrigerator for 30 to 45 minutes.

Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

Once chilled, use a cookie scoop to portion out balls of dough about 1.5 inches in diameter.

Bake cookies for 11-14 minutes, or until edges are golden brown and centers remain soft.

Let cookies cool on the baking sheet for about 5 minutes before transferring to a wire rack.