Ingredients

Step by step

1. Preheat the oven to 170°C, fan 150°C, gas 3. Grease a 20cm round deep cake tin and line the base and sides with baking paper.
2. Pour the milk into a jug and add the lemon juice. Set aside for 15 minutes – the milk will start to curdle slightly. Sift the flour, bicarbonate of soda, cocoa powder and mixed spice into a bowl.
3. Place the butter and sugar in a large mixing bowl and beat with a hand-held electric whisk until pale and creamy. Gradually beat in the eggs, then fold in the flour and milk mixtures until thoroughly combined. Fold in the melted chocolate.
   Tip

    
4. Spoon the mixture into the prepared tin and gently level the surface. Bake for 1 hour 20 minutes – 1 hour 30 minutes until the cake is risen, firm to the touch and a skewer inserted into the cake comes out clean. Leave to cool in the tin for 10 minutes, then turn out onto a wire rack and leave to cool completely.
5. To make the buttercream, place the butter in a bowl and beat with an electric hand-held whisk until very soft and creamy. Gradually beat in the icing sugar and vanilla extract.
6. Use a serrated knife to slice the cake in half horizontally. Sandwich the cake back together with two-thirds of the buttercream and spread the rest over the top and sides of the cake in a thin layer. Place the cake on a sheet of baking paper on a board and decorate.