Chocolate mousse cake

Method

1. Heat the oven to 160°C fan/gas 4 and grease and line the base and sides the cake tin with butter/oil and baking paper. Melt the dark chocolate in a heatproof bowl over a pan of barely simmering water (don’t let the base of the bowl touch the water) then set aside to cool slightly. In a large mixing bowl, combine the flour, cocoa, sugar, raising agents and salt. In a jug, whisk the oil and egg until combined, then whisk in the milk.
2. Pour the wet ingredients and melted chocolate into the dry and stir to combine. Pour over 80ml just-boiled water (you can use the water from the pan used to melt the chocolate) and mix to combine. Tip the batter into the prepared tin and bake for 16-18 minutes, until a skewer inserted into the centre comes out with only a few damp crumbs. Set the tin on a wire rack to cool.
3. Once the cake is almost cool, make the mousse. Melt the dark and milk chocolate in a large bowl over a pan of barely simmering water (don’t let the base of the bowl touch the water). Set aside to cool until lukewarm. With an electric whisk, beat the egg whites in a bowl to stiff peaks. In another bowl, whisk the whipping cream almost to soft peaks (be careful not to overwhip it as it will stiffen further when mixed with the other ingredients).
4. Working quickly to avoid the chocolate becoming grainy, stir the egg yolks into the lukewarm chocolate, then mix in the whipped cream. Gently fold in the egg whites. Spread the mixture over the cake in the tin and chill overnight.
5. Remove from the tin and carefully peel away the baking paper to serve, decorated with mini eggs (or whatever you fancy).