Add the butter to a light-colored saucepan over medium heat. Stir frequently until the butter foams and deep golden brown bits form at the bottom of the pan. The butter should smell nutty and caramel-like. Immediately remove from the heat and pour into a large heatproof bowl.
Cool the browned butter for about 20 minutes until warm but not hot.
Whisk in the dark brown sugar and granulated sugar until smooth and glossy.
Add the egg, egg yolk, and vanilla extract. Whisk vigorously for about 1 minute until fully emulsified and slightly thickened.
In a separate bowl, whisk together the flour, cornstarch, baking soda, salt, and cinnamon.
Fold the dry ingredients into the wet ingredients until almost combined.
Fold in the white chocolate chips, finely chopped candy corn, and cookie crumbs just until evenly distributed.
Cover and chill the dough for at least 1 hour. Overnight chilling gives the best flavor and texture.
Preheat the oven to 350°F. Line baking sheets with parchment paper.
Scoop large 2-tablespoon portions of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake for 10–11 minutes or until the edges are lightly golden and the centers still look slightly underbaked.
Sprinkle lightly with flaky sea salt immediately after baking if desired.
Cool on the baking sheet for 8–10 minutes before transferring to a wire rack.