Brown Butter-Mocha Cookies

In a small saucepan, melt the butter over low heat, whisking constantly. When butter is fully melted, raise the heat to medium and continue whisking until butter starts to turn brown and starts to smell nutty, about 2 to 3 minutes. Pay close attention because the butter can easily burn. Pour into the bowl of a stand mixer with the oil and place in the fridge until it returns to room temperature and is a little solid, about 25 to 30 minutes.
In a small mixing bowl, combine the flour, coffee powder, cocoa powder, salt (if using), baking soda, baking powder, and cornstarch. Mix well.
After the butter has cooled, add the sugars to the bowl and cream with the mixer until light and fluffy, about 4 minutes. Slowly add in the egg and vanilla and beat until fully combined. Add in the entire flour mixture and mix slowly until just combined. Do not overmix. Fold in chopped chocolate.
Cover the dough with plastic wrap and let chill in the fridge for at least an hour, but preferably overnight.
Preheat oven to 350u0b0 F. Take cookie dough out of the fridge. If the dough is too hard to scoop, let stand at room temperature until malleable, 10 to 15 minutes.
Using a cookie scoop, scoop out dough onto a parchment-lined baking sheet. Bake at 350u0b0 F for 8 minutes, then turn off the oven without opening it, keeping the cookies inside, and leave for 2 minutes. Remove from oven and let cool before eating.