Make the browned butter (see note below), or re-melt browned butter if it is already made. Once melted, add instant espresso and mix in. Set aside for about 20 minutes to allow the butter espresso mixture to infuse and cool.
3/4 cup browned butter, 1/2 teaspoon instant espresso powder
In a medium bowl, sift the flour, baking soda and salt to combine.
2 cups all-purpose flour, 1/2 teaspoon baking soda, 1/2 teaspoon kosher salt
Add the brown butter mixture, brown sugar, light brown sugar and white sugar to a large bowl and mix until well blended.
1/2 cup loosely packed dark brown sugar, 1/2 cup loosely packed light brown sugar, 1/2 cup granulated sugar
Next, add 1 egg and beat the ingredients together for 1-2 minutes. Then add the egg yolk and vanilla extract and beat for another 1-2 minutes.
1 egg + 1 egg yolk, 2 teaspons vanilla extract
Add the dry ingredients to butter, sugar and egg mixture, and mix just until the ingredients are combined. You want to be careful not to over mix as it will impact the texture of the cookies.
Gently stir in the chocolate chunks and chocolate chips. It is not necessary to use both chunks and chips, but we personally like to incorporate both to add some variety to the texture.
8 ounces bittersweet chocolate bar, 2/3 cup milk chocolate chips
Scoop out about 1/3 cup of the dough and roll into balls.
Place on a baking sheet. At this point you can bake or refrigerate the dough overnight. If you are in a time crunch, you can refrigerate for just 30 minutes, but the longer you wait the better they will turn out!
Preheat your oven to 350 degrees Fahrenheit.
Remove the chocolate chip cookie batter from the fridge.
Place on a non-stick baking sheet about 2 inches apart from each other so they have room to expand in the oven.
When your oven is heated, bake the cookies on the center rack for 14-16 minutes, or until the edges are golden brown. Make sure not to overbake the cookies as they will continue to cook from the residual heat after they come out of the oven.
After a couple minutes, transfer the cookies to a wire rack and allow them to cool. Sprinkle with maldon salt, or your favorite flaky sea salt!
maldon salt flakes for garnish