Ingredients:

  • 2 cups All-Purpose Flour (Plain flour)
  • 2 cups Granulated Sugar (Caster sugar is fine too)
  • 1/2 cup Unsweetened Cocoa Powder (High-quality Dutch-process preferred)
  • 1 tsp Baking Soda (Bicarbonate of soda)
  • 1 tsp Kosher Salt (Or 1/2 tsp fine sea salt)
  • 1 cup Unsalted Butter, diced (225 g)
  • 1 cup Boiling Water or Coffee (240 ml)
  • 1/2 cup Buttermilk, cold (120 ml)
  • 2 large Eggs, lightly beaten (~100 g)
  • 1 tsp Vanilla Extract (5 ml)
  • -- For the Cooked Fudge Frosting ---
  • 1/2 cup Unsalted Butter, diced (115 g)
  • 1/4 cup Unsweetened Cocoa Powder (25 g)
  • 1/3 cup Whole Milk (80 ml)
  • 1 tsp Vanilla Extract (5 ml)
  • 3 cups Powdered Sugar, sifted (Icing sugar, 360 g)
  • Pinch Salt (To balance sweetness)

Instructions:

  1. Preheat oven to 175°C (350°F). Lightly grease and flour the 9x13 inch pan, or line it with parchment paper for easy removal.
  2. In a large mixing bowl, whisk together the flour, granulated sugar, 1/2 cup cocoa powder, baking soda, and salt until thoroughly combined. Set aside.
  3. In a small saucepan, melt the 1 cup of butter. Add the 1 cup of boiling water (or coffee) to the melted butter and stir briefly.
  4. Pour the hot butter/liquid mixture directly into the dry ingredients and whisk until just combined.
  5. Whisk the buttermilk, lightly beaten eggs, and vanilla extract together in a separate small bowl. Pour this mixture into the main batter and mix until smooth, scraping down the sides. The batter will be thin.
  6. Pour the batter into the prepared pan. Bake for 20–25 minutes, or until a toothpick inserted into the centre comes out with moist crumbs attached.
  7. Remove the cake from the oven and place it on a wire rack. Let it cool for 10–15 minutes. The cake needs to be warm, not piping hot, when frosted.
  8. In the saucepan, melt the remaining 1/2 cup butter. Stir in the 1/4 cup cocoa powder and the milk. Bring the mixture to a rolling boil over medium heat, stirring constantly. Remove immediately from the heat.
  9. Whisk in the vanilla extract and salt. Gradually add the sifted powdered sugar, one cup at a time, mixing until smooth and glossy. Work quickly, as this frosting sets fast.
  10. While the cake is still warm and the frosting is still liquid, pour the frosting evenly over the entire surface of the cake. Use a spatula to quickly spread it to the edges.
  11. Allow the cake to cool fully on the rack for at least 30 minutes before slicing and serving, allowing the fudge frosting to set into a beautiful crust.