In a large mixing bowl, combine melted and slightly cooled unsalted butter with both granulated and brown sugars. Beat on medium speed until light and fluffy, about 2-3 minutes.

Add eggs one at a time, mixing well after each addition. Pour in vanilla extract and blend until smooth.

In a separate bowl, whisk together flour, cinnamon, cornstarch, baking soda, and baking powder. Gradually add to wet ingredients, mixing on low speed until just combined.

Gently fold in chopped pecans and toffee bits (if using) with a spatula.

Wrap the dough in plastic wrap and refrigerate for 30-45 minutes.

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

Use a cookie scoop to portion out and roll each scoop into a ball, optionally rolling in granulated sugar.

Place dough balls on the prepared baking tray, 2 inches apart. Bake for 11-14 minutes until edges are golden and centers are slightly soft.

Allow cookies to cool on the tray for 5 minutes before transferring to a wire rack.