Step‑by‑Step Instructions

• Preheat your oven to 350ºF (180ºC). Grease a 9-inch springform pan, and line the bottom with parchment paper.
• Whisk together flour, cocoa powder, espresso powder, baking powder, baking soda, and sea salt in a small bowl.
• In a large bowl, whisk together sugar, oil, sour cream, egg, and vanilla until smooth and combined.
• Sift dry ingredients into wet mixture, whisking gently. Add boiling water gradually and mix until smooth.
• Pour batter into prepared pan and bake for 24 to 28 minutes until a toothpick comes out clean.
• Cool the cake on a wire rack for 15 minutes, then remove from pan and cool completely.
• Whisk together cream, egg, yolk, sugar, cocoa powder, espresso powder, and salt in a saucepan off the heat.
• Place saucepan over low heat, whisking constantly for 8 to 10 minutes until mixture reaches 170ºF (76ºC).
• Remove from heat, add chopped dark chocolate and vanilla, whisk until smooth.
• Chill chocolate mixture in fridge for 1 to 1.5 hours until thick and spreadable.
• Whip cold cream in another bowl until firm peaks form. Fold into the cooled chocolate mixture.
• Spread the mousse over the cooled cake in the pan and chill for at least 8 hours.
• For ganache, place chocolate in a bowl, heat cream in a saucepan, pour over chocolate, and stir until smooth.
• Remove cake from fridge, pour ganache over it, chill another 10 to 15 minutes before serving.