Make the browned butter (see note below) and add instant espresso, letting it infuse and cool for about 20 minutes.
In a medium bowl, sift together flour, baking soda, and salt.
In a large bowl, mix browned butter, brown sugar, light brown sugar, and white sugar until well blended.
Add 1 egg, beat for 1-2 minutes; then add egg yolk and vanilla extract, beat for another 1-2 minutes.
Add dry ingredients to the butter-sugar-egg mixture, mixing just until combined (avoid overmixing).
Gently stir in chocolate chunks and chocolate chips.
Scoop out about 1/3 cup of dough, roll into balls, and place on a baking sheet. Refrigerate if time allows.
Preheat oven to 350 degrees.
Place cookie dough balls on a non-stick baking sheet, 2 inches apart.
Bake for 14-16 minutes until edges are golden brown. Avoid overbaking.
Transfer cookies to a wire rack to cool. Sprinkle with Maldon salt or your favorite flaky sea salt.