Ingredients:

  • 1 ½ cups (190g) all-purpose flour
  • ¾ cup (60g) unsweetened cocoa powder
  • 1 ½ teaspoons baking powder
  • 1 ½ teaspoons baking soda
  • ¾ teaspoon salt
  • 1 ½ cups (300g) granulated sugar
  • ¾ cup (180ml) buttermilk, at room temperature
  • ¾ cup (180ml) vegetable oil (canola or sunflower)
  • 2 large eggs, at room temperature
  • 2 teaspoons vanilla extract
  • ¾ cup (180ml) boiling water
  • 8 ounces (225g) good-quality bittersweet chocolate (60-70% cacao), chopped
  • 1 cup (240ml) heavy cream, cold
  • 2 large eggs, separated
  • ¼ cup (50g) granulated sugar
  • 4 ounces (115g) semi-sweet chocolate, chopped
  • ½ cup (120ml) heavy cream

Instructions:

  1. Grease and flour two 8-inch round cake pans, line the bottoms with parchment paper.
  2. Whisk together flour, cocoa powder, baking powder, baking soda, and salt in a large bowl.
  3. In a separate bowl, whisk together sugar, buttermilk, oil, eggs, and vanilla extract.
  4. Gradually add the wet ingredients to the dry ingredients, mixing until just combined.
  5. Slowly pour in the boiling water while mixing on low speed. The batter will be thin.
  6. Divide the batter evenly between the prepared cake pans and bake at 350°F (175°C) for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
  7. Let the cakes cool in the pans for 10 minutes, then invert them onto a wire rack to cool completely.
  8. Melt the chocolate in a double boiler or heatproof bowl set over simmering water, stirring until smooth. Remove from heat and let cool slightly.
  9. In a chilled bowl, beat the heavy cream with a mixer until stiff peaks form.
  10. In a separate bowl, beat the egg yolks and sugar until pale and thick.
  11. In a clean, dry bowl, whisk the egg whites until stiff peaks form.
  12. Gently fold the melted chocolate into the yolk mixture, then fold in the whipped cream, followed by the egg whites. Be careful not to deflate the mixture.
  13. Place one cake layer on a serving plate. Spread the chocolate mousse evenly over the cake layer. Top with the second cake layer.
  14. Refrigerate the cake for at least 1 hour to allow the mousse to set.
  15. Heat the heavy cream in a saucepan until simmering. Pour the hot cream over the chopped chocolate and let it sit for 1 minute. Whisk until smooth.
  16. Pour the ganache over the cake, allowing it to drip down the sides.
  17. Refrigerate for another 30 minutes to allow the ganache to set.
  18. Slice and serve cold.