Preparation Steps

• Brown the butter: melt unsalted butter in a light-colored saucepan over medium heat. Swirl frequently; it will foam, then the milk solids will turn golden and smell nutty. Remove from heat as soon as you see amber specks and a toasted aroma, then pour into a heatproof bowl and let cool 8–10 minutes.
• Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
• Whisk the dry ingredients (flour, baking soda, and salt) together in a medium bowl and set aside.
• In a large bowl, combine the warm browned butter with both sugars and stir until mostly smooth. Add the vanilla, then whisk in the whole egg and the two yolks until the mixture is glossy and slightly thickened.
• Fold the flour mixture into the butter-sugar base with a spatula just until there are no large streaks of flour — do not overmix. Then gently fold in the chopped dark chocolate and semi-sweet chips so they’re distributed but the dough remains slightly shaggy.
• Cover the bowl and chill the dough in the refrigerator for 30 minutes. Chilling firms the dough so the cookies spread less and stay chewy in the center.
• Portion the dough: using a 2-tablespoon scoop or a rounded tablespoon, drop mounds of dough onto the prepared sheet about 2 inches apart. Press a few extra chocolate pieces onto the top of each ball for a rustic look if you like.
• Bake on the middle rack for 11–13 minutes, until the edges are set and just beginning to brown but centers still look soft. Rotate the pan once halfway through for even browning.
• Let the cookies rest on the baking sheet for 5 minutes so they finish setting, then transfer to a wire rack to cool completely. Store in an airtight container at room temperature for up to 4 days.