40g vegetable oil
10g cocoa powder
1g ground coffee
15g dark chocolate
38g cake flour
45g granulated sugar
- Mix vegetable oil, cocoa powder, and ground coffee until well combined. Add in milk, whisk until well combined. Add in cake flour, mix until smooth. Add in 4 egg yolks and melted dark chocolate, mix until well combined.
- Add in lemon juice and granulated sugar into the egg white, and use a hand mixer to beat until it forms soft peaks. Take a scoop of whipped egg white to mix with the batter first until just combined, and then pour all the batter into the whipped egg white to mix until just combined.
- Line the baking tray (28*28cm), pour all the batter into the baking tray, and give the pan a few taps before send into the oven. Preheat the oven to 302℉（150℃）and bake for 25 minutes.
- Let the cake cool down on the cooling rack.
2g ground coffee
215g heavy cream
20g granulated sugar
100g mascarpone cheese
- Put ground coffee, 15g heavy cream, sugar, and mascarpone cheese together and beat until smooth.
- Add in 200g heavy cream, beat until thickened.
Assemble the Cake
- Let the cake cool down on the cooling rack and then peel off the parchment paper or baking mat.
- Put the filling onto the cake, smooth it, and roll the cake up. Let the cake cool in the fridge for half an hour until set.
- Decorate the cake with rest of the filling. Dust with powdered sugar and cocoa powder. Decorate with chocolate and rosemary (optional).