Brown 1/2 of the butter. This should be 75 grams or 5.5 tablespoons. In a saucepan over medium heat cook the butter until it gets a deep dark brown color. Then pour that browned butter into a bowl to cool. Add in the other half of your room temp butter and mix. At this point, you’re looking for the mixture to become homogenous. If it is too loose, you can place it in the fridge for about 20 minutes and whisk it until combined. It should solidify and have a whipped texture.
To your butter add in your brown sugar, white sugar and vanilla. Mix until fluffy (I recommend a stand mixer, by hand works but it will take about 10 min by hand)
Next, add your eggs. Mix thoroughly, the mixture will get thicker as you mix, that’s what you want!
Divide batter into two separate bowls, one will be for the chocolate and one for the vanilla. It is tough to eyeball so know that each should weigh around 220 g.
In one of the bowls, add 110 grams flour, 1/4 tsp baking powder and 1/4 tsp salt and fold using a spatula. Add milk chocolate and fold. Reserve some of your chocolate for the top of the cookie!
Next, in the other bowl, add 75 g flour, 25 g cocoa powder, instant coffee (if using) 1/4 tsp baking powder and 1/4 tsp salt Add chopped white chocolate and fold. Reserve some of your chocolate for the top of the cookie
Preheat your oven to 350 F.
To form the cookies, you can use your hands or a cookie scoop. I like to scoop little portions of each dough, alternating between the two. If you prefer, you can also form two small dough balls, mash them to tether and roll them again into a ball.
Bake for 10-12 minutes or until the sides have started browning slightly.