Indulge in this delightful chocolate and mascarpone sponge cake, a truly comforting treat that's surprisingly easy to bake. The rich chocolate custard filling adds a luscious creaminess, making every bite a moment of pure bliss.
Preheat your oven to 180°C (160°C fan/Gas Mark 4). Grease and flour a 20 cm round cake tin. Separate the eggs, placing the yolks in one bowl and the whites in another. Sift together the plain flour, cocoa powder, and baking powder.
In a large bowl, whisk the mascarpone with 100g of the caster sugar until light and fluffy. Gradually beat in the egg yolks one by one. Gently fold in the sifted dry ingredients until just combined. In a separate clean bowl, whisk the egg whites until stiff peaks form, then carefully fold them into the cake batter in two additions, being careful not to deflate the mixture.
Pour the cake batter into the prepared tin and bake for 35-40 minutes, or until a skewer inserted into the centre comes out clean. Let it cool in the tin for 10 minutes before turning it out onto a wire rack to cool completely.
While the cake cools, prepare the chocolate custard. In a saucepan, whisk together the milk, remaining 100g caster sugar, and cornflour until smooth. Heat over a medium heat, stirring constantly, until the mixture thickens. Remove from the heat and stir in the dark chocolate until melted and smooth. Let the custard cool slightly.
Once the cake is completely cool, slice it horizontally into two or three layers. Spread the chocolate custard evenly between the layers.
Dust the top of the cake generously with icing sugar before serving.
Ensure your mascarpone is at room temperature for easier mixing and a smoother batter.
For an extra rich flavour, use high-quality dark chocolate with at least 70% cocoa solids for the custard.
To prevent the cake from sticking, line the bottom of your cake tin with baking parchment in addition to greasing and flouring.