INGREDIENTS:
For the chocolate cake:
2/3 cup (150ml) sour cream or crème frâiche
2 eggs
1 1/2 teaspoons vanilla extract or vanilla bean paste
1 1/3 cups (200g) plain flour (all-purpose flour)
1/3 cup (40g) cocoa powder
1 cup (200g) caster sugar (superfine sugar)
3/4 teaspoon baking powder
1/4 teaspoon baking soda
1/2 teaspoon fine salt
2 sticks (200g) unsalted butter, softened
For the sour cream chocolate frosting:
3 oz (80g) milk chocolate (semi-sweet chocolate e.g. 42% cocoa)
3 oz (80 g) dark chocolate (bittersweet chocolate, e.g. 70% cocoa)
3/4 stick (75g) unsalted butter
1/2 cup (125ml) sour cream or crème frâiche
1 teaspoon vanilla extract or vanilla bean paste
1 tablespoon golden syrup (or light corn syrup)
2 1/4 cups (300g) icing sugar (powdered sugar), sifted
INSTRUCTIONS:
Preheat the oven to 180°C (350°F) (without fan).
Line and grease 2 x 20cm (8 inches) round cake pans.
In a small bowl or jug, lightly whisk together the sour cream, eggs and vanilla extract.
Place the flour, cocoa powder, sugar, baking powder, baking soda, salt, and butter into the bowl of an electric stand mixer with the flat paddle attachment.
Beat on low speed until the butter is incorporated into the dry ingredients. The mixture should resemble crumbly, wet sand.
Slowly add the egg mixture and beat until the batter is thoroughly mixed.
Pour the batter evenly into the prepared cake pans.
Bake for about 25 to 30 minutes, or until a skewer inserted in the middle comes out clean.
Place the cake pans on a wire rack and let the cakes cool in the pans for about 10 minutes, before turning them onto the wire rack to cool completely.
For the sour cream chocolate frosting:
To make the frosting, melt the chocolate and butter in a bain-marie or a bowl over a pan of simmering water, taking care not to let the bowl come into contact with the water.
Once the chocolate has melted, take the bowl off the heat.
Stir in the sour cream, vanilla extract, and golden syrup.
Measure the icing sugar (powdered sugar) into the bowl of an electric stand mixer.
Using the flat paddle attachment, slowly beat the chocolate mixture into the icing sugar (powdered sugar).
The frosting should be thick enough to cover the cake, but soft enough to spread easily.
To assemble the cake:
Cut four thick strips of baking paper and place them on a large plate or cake stand in the shape of a square. The baking paper is to help keep the serving plate clean while you are frosting the cake.
Place one cake on top of the baking paper.
Spread about 1/3 of the frosting over the cake in a thick layer.
Place the second cake on top and spread another 1/3 of frosting over the cake.
Use the remaining frosting to cover the sides of the cake.
Once you have finished frosting the cake, carefully remove the pieces of baking paper.
Leave the cake to set for at least 1 hour before serving.