Ingredients:

  • 125g all-purpose flour
  • 200g granulated white sugar
  • 30g unsweetened Dutch-processed cocoa powder
  • 10g baking powder
  • 2g fine sea salt
  • 120ml whole milk
  • 60g unsalted butter, melted
  • 5ml pure vanilla extract
  • 100g light brown sugar, packed
  • 100g granulated white sugar
  • 30g unsweetened Dutch-processed cocoa powder
  • 350ml boiling water

Instructions:

  1. Preheat your oven to 350°F (180°C). In your large bowl, whisk together the 125g flour, 200g granulated sugar, half of the cocoa powder (15g), baking powder, and sea salt. Note: Whisking dry ingredients first prevents cocoa clumps in the finished cake.
  2. Stir in the 120ml milk, 60g melted butter, and 5ml vanilla extract. Mix until the batter is thick and smooth.
  3. Spread this evenly into your ungreased baking pan using a spatula.
  4. In a separate small bowl, combine the 100g brown sugar, the remaining 100g white sugar, and the remaining 15g cocoa powder. Sprinkle this mixture liberally and evenly over the top of the batter.
  5. Carefully pour the 350ml boiling water over the back of a spoon onto the sugar layer. Note: Using a spoon breaks the fall of the water so it doesn't wash a hole into the batter. DO NOT STIR. Leave the mess exactly as it is.
  6. Bake for 35 minutes until the top is firm and crackly. The center should have a slight jiggle, and you’ll see the dark chocolate sauce bubbling up around the edges of the pan.