In a medium saucepan, melt the butter over medium heat. Once it starts boiling, gently stir with a wooden spoon or swirl the pan continuously. After a couple of minutes it will turn from light yellow to a deep golden, honey color.
1/2 cup butter
Once small brown bits form and it smells nutty, it's ready. It burns very quickly at this point, so don't walk away.
Immediately transfer the brown butter to a heatproof bowl and refrigerate for about 1 hour, until solid.
Make the Cookie Dough
Transfer the solid brown butter to your stand mixer bowl. Add both sugars and cream for about 2 minutes. Add the egg and vanilla and mix until well incorporated.
1/2 cup packed brown sugar, 1/4 cup granulated sugar, 1 egg, 2 tsp vanilla extract
Add the flour, cornstarch, baking soda, and salt and stir just until combined. Avoid overmixing. Fold in the peanuts and whole candy corn.
1 1/8 cup all purpose flour, 1/2 tsp baking soda , 1/2 tsp salt, 1 cup peanuts, 1 cup candy corn, 1 tbsp cornstarch
Refrigerate the dough (about 15 minutes) while you preheat the oven to 350°F (175°C).
Scoop and Bake
Scoop the dough with a large cookie scoop or 1/4 cup measure onto a baking sheet lined with parchment or a silicone mat. Tuck any candy corn touching the pan back into the dough.
Bake for 10 to 11 minutes, until the edges are golden brown. Press extra candy corn into the tops right away, if using.
Cool on the baking sheet for 10 minutes, then transfer to a cooling rack.
Notes
Candy corn touching the baking sheet melts and spreads. Tuck edge pieces into the dough before baking, and add topping candy corn right after baking.
Salted or unsalted butter both work. Use salted peanuts for the full sweet and salty flavor.
Weighing the flour (145 g) is the easiest way to avoid dry or flat cookies.
Store in an airtight container for up to a week, or in the fridge or freezer for longer. Thaw frozen cookies in the fridge, then bring to room temperature.