Ingredients:

  • 1/2 cup (115g) unsalted butter, melted and hot
  • 4 oz (113g) semi-sweet chocolate (60% cacao), finely chopped
  • 1/4 cup (25g) Dutch-processed cocoa powder, sifted
  • 1 tsp espresso powder
  • 3/4 cup (150g) granulated sugar
  • 1/4 cup (50g) light brown sugar, packed
  • 2 large eggs, room temperature
  • 1 tbsp vanilla bean paste or extract
  • 1/2 cup (65g) all-purpose flour
  • 1/2 tsp flaky sea salt

Instructions:

  1. Preheat your oven to 350°F (175°C). Line an 8x8-inch metal baking pan with parchment paper, leaving an inch of overhang on two sides to create a sling.
  2. In a heat-proof bowl, combine the hot melted butter, chopped semi-sweet chocolate, sifted cocoa powder, and espresso powder. Whisk until the chocolate is completely smooth and the cocoa has bloomed in the fat.
  3. In a separate large bowl, combine granulated sugar, light brown sugar, eggs, and vanilla. Use an electric hand mixer to beat the mixture for a full 5 minutes until it reaches the 'ribbon stage'—it should be pale, thick, and fall in ribbons.
  4. Whisk the cooled chocolate-butter mixture into the egg foam until just combined.
  5. Sift the flour and sea salt over the wet ingredients. Use a spatula to gently fold the dry ingredients into the batter until no white streaks remain, being careful not to deflate the aeration.
  6. Pour the batter into the prepared pan and smooth the top. Bake for 22–25 minutes. The center should be set but still slightly moist—do not overbake if you want a fudgy result.
  7. Top with an extra pinch of flaky sea salt and allow to cool completely in the pan before lifting out with the parchment sling and slicing into 16 squares.