Chocolate and Malteser cake

Method

1. Heat the oven to 180°C/fan160°C/gas 4. Grease and line 2 deep 20cm cake tins with baking paper. Put the 225g butter and the caster sugar in a large mixing bowl and beat with an electric hand mixer until light and fluffy (or use a stand mixer). Add the eggs, one at a time, beating well after each addition. Add the melted dark chocolate and the golden syrup and beat well.
2. Sift the dry ingredients into another mixing bowl and set aside. In a jug, mix the milk, soured cream and vanilla extract. Beat a third of the dry mixture into the dark chocolate mixture, then add half the milk mixture. Beat well, then repeat with another third of the dry mixture and the remaining milk mixture. Finish with the final third of the dry mixture. Fold the crushed Maltesers into the batter, then divide it evenly between the prepared tins.
3. Bake in the middle of the oven for 1 hour or until a skewer pushed into the centre of the sponges comes out almost clean. Allow to cool in the tins for 5 minutes before turning out onto a wire rack to cool completely.
4. For the icing, put the 450g butter and the icing sugar in a mixing bowl and beat together with an electric hand mixer until light and fluffy. Add the 4 tbsp malted milk powder and the rum and beat well. Gradually pour in the cooled melted white chocolate and cream mixture, beating until smooth (see Make Ahead and Know-how).
5. Using a long serrated knife and a thread, carefully slice each sponge in half through the middle so you have 4 layers (keep the one with the neatest, flattest base for the top). Put one of the sponge layers on a cake stand or serving plate, cut-side up, then spread with an eighth of the icing. Top with a second layer of sponge, cut-side down, then spread again with another eighth of the icing. Repeat with the final 2 layers of sponge, both cut-side down. Use a palette knife to cover the outside of the cake with the remaining icing, then decorate the top to serve.