Ingredients:

  • 1 cup (2 sticks) unsalted butter, softened
  • ¾ cup packed light brown sugar
  • ½ cup granulated sugar
  • 1 large egg, room temperature
  • 1 large egg yolk, room temperature
  • 2 teaspoons vanilla extract
  • 2 cups all-purpose flour
  • ½ cup Dutch-processed cocoa powder
  • 1 teaspoon baking soda
  • 1 teaspoon fine sea salt
  • 1 cup semisweet chocolate chips
  • 1 cup dark chocolate chunks (60–70% cacao)

Instructions:

  1. Prep the Oven and Pan: Preheat oven to 375°F (190°C). Line two large baking sheets with parchment paper or silicone mats.
  2. Combine Dry Ingredients (excluding sugars): In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
  3. Cream Butter and Sugars: In the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter, brown sugar, and granulated sugar on medium speed for 3–4 minutes until light and fluffy.
  4. Add Eggs: Add the whole egg, then the extra egg yolk, followed by the vanilla extract. Beat until just combined, scraping down the sides of the bowl as needed.
  5. Incorporate Dry Mix: With the mixer on low speed, gradually add the dry ingredient mixture to the wet ingredients. Mix only until the flour streaks just disappear. Stop mixing immediately to avoid developing gluten.
  6. Fold in Chocolate: Remove the bowl from the mixer and use a rubber spatula to fold in both the semisweet chocolate chips and dark chocolate chunks. Distribute the chocolate evenly throughout the dough.
  7. Chill the Dough (The Key Step): Scoop the dough using a 3-tablespoon scoop and place the dough balls onto a plate or small sheet tray. Cover and refrigerate for a minimum of 60 minutes.
  8. Arrange and Bake: Place 6–8 chilled dough balls onto the prepared baking sheets, ensuring they are spaced well apart.
  9. Bake: Bake for 10–12 minutes at 375°F (190°C). The cookies are done when the edges are set but the centers still look slightly soft, puffy, and glossy.
  10. Cool: Remove the sheets from the oven. Let the cookies cool on the sheet pan for 5 minutes before carefully transferring them to a wire rack to cool completely. This crucial resting period prevents the cookies from collapsing.