In a large bowl using an electric handheld mixer on high speed, cream the softened butter and brown sugar together for 1 minute. The mixture should be smooth, creamy, and lightly golden in colour. Add the vanilla and mix just until combined.
Add the flour and cornstarch and mix, starting on low speed and increasing to high speed. Beat on high speed for 30 seconds or until whipped and creamy. Fold in the chopped nuts.
Cut an 18-inch long piece of wax paper and place it on the counter. Transfer the cookie dough to the wax paper and shape/roll into a log about 1 ½ inches in diameter. Place on a cookie sheet or flat surface and refrigerator for 1 hour.
Preheat the oven to 350℉. Line baking sheet(s) with parchment paper or silicone baking mats. Take the chilled cookie dough log out of the refrigerator and unwrap the wax paper. Using a sharp knife, slice the log into ¼-1/2-inch slices. Place each slice on the prepared baking sheets, leaving 1 inch between each cookie for spreading room. Bake in the preheated oven for 12-16 minutes or until lightly golden. Let cool on the pan for 10 minutes before transferring to a wire rack to finish cooling before topping with the melted chocolate.
Drizzle melted chocolate of your choice over the fully cooled cookies. Place in the refrigerator or a cool place to allow the chocolate to firm up. Enjoy!
Notes
Store cookies in an airtight container at room temperature for up to 5 days.