Ingredients:

  • 1 cup (225g) Unsalted butter, melted and warm
  • ¾ cup (75g) Dutch-processed cocoa powder
  • ½ cup (90g) Semisweet chocolate chips
  • 1 cup (200g) Granulated white sugar
  • ¾ cup (150g) Packed light brown sugar
  • 3 Large eggs, room temperature
  • 1 Large egg yolk, room temperature
  • 1 tablespoon Pure vanilla extract
  • 1 teaspoon Espresso powder
  • ¾ cup (95g) All-purpose flour
  • ½ teaspoon Sea salt
  • ½ cup (90g) Semi-sweet chocolate chunks

Instructions:

  1. Preheat your oven to 350°F (175°C). Line an 8x8 inch metal baking pan with parchment paper, leaving an overhang on the sides for easy removal.
  2. In a large heat-proof glass bowl, combine the warm melted butter, Dutch-process cocoa powder, and 1/2 cup semisweet chocolate chips. Whisk until the chocolate has melted and the cocoa is 'bloomed' and smooth.
  3. Add the granulated white sugar and light brown sugar to the butter mixture. Whisk vigorously to begin dissolving the sugar crystals.
  4. Add the 3 large eggs, the additional egg yolk, and vanilla extract. Whisk the batter intensely for 2 full minutes. This emulsification process is vital for creating the crackly, shiny top.
  5. Using a silicone spatula, gently fold in the all-purpose flour, sea salt, espresso powder, and the remaining 1/2 cup of chocolate chunks until no streaks of flour remain. Do not overmix.
  6. Pour the batter into the prepared pan and smooth the top. Bake for 25 minutes. The center should be set but still slightly soft to the touch.
  7. Remove from the oven and allow to cool completely in the pan before slicing. This allows the fudgy structure to set fully.