Add the melted butter and brown sugar to a mixing bowl and stir together well.
3/4 cup melted butter, cooled, 1 1/3 cup brown sugar
Add the egg, egg yolk and vanilla to the bowl and stir again.
1 egg, 1 egg yolk, 1 Tablespoon vanilla extract
Add the salt, flour, coffee powder, and baking soda to the bowl and stir to make a thick dough.
1/2 teaspoon salt, 1 3/4 cup flour, 1/2 teaspoon baking soda, 1/4 cup instant coffee powder
Fold in the chocolate chips.
1 cup chocolate chips
Refrigerate the cookie dough for one hour or longer.
Preheat your oven to 350ºF and line a baking tray with parchment paper.
Scoop the cookies into two tablespoon-sized balls (use a spring-loaded cookie scoop if possible for uniform cookies). Place the cookie dough balls on the parchment-lined tray at least 2 inches apart.
Bake the cookies for 11 minutes. The edges will be browning but the center will be soft and puffed up.
Let the cookies cool for 5 minutes on the baking tray then move to a cooling rack. Enjoy!