I made this cake with my friend last week for her sister's birthday but I never got to try a proper slice :( so I decided to bake it again yesterday because my mum & dad were coming back from their holiday. It is so delicious, quite dense and rich really. The buttercream is delicious. It has 'horlicks' in it, which I'm not sure you can get outside the UK. It's malt powder I think? Anyway, mixed with the cocoa it gives it a taste like malteasers! So so good. The recipe is from here - http://www.aspoonfulofsugar.net/blog/2005/01/chocolate_malteser_birthday_ca.html but it's actually from Nigella Lawson's Feast.
Chocolate Malteser Cake
From "Feast", Nigella Lawson (2004)
For the cake
150g soft brown sugar (muscavado sugar is best for flavour)
100g caster sugar
3 large eggs
15g unsalted butter
2 tablespoons Horlicks powder
175g plain flour
25g cocoa, sieved
1 teaspoon baking powder
1/2 teaspoon bicarbonate of soda
For the icing and decoration
250g icing sugar
1 teaspoon cocoa
125g soft unsalted butter
2 tablespoons boiling water
2 x 37g packets Maltesers
Take whatever you need out of the fridge so that all the ingredients can come to room temperature (though it's not so crucial here, since you're heating the milk and butter and whisking the eggs.
Preheat the oven to Gas Mark 3/170C. Butter and line two 20cm loose-bottomed sandwich cake tins with baking parchment.
Whisk together the sugars and eggs until light and frothy. Heat the milk, butter and Horlicks powder in a small saucepan until the butter has melted and the mixture is hot but not boiling. Beat the milk mixture into the eggs a little at a time. Fold in the dry ingredients thoroughly. Divide the cake batter evenly between the two tins and bake in the oven for 25 minutes, by which time the cakes should have risen and will spring back when pressed gently. Let them cool on a rack for about 5-10 minutes and then turn them out of their tins.
Once the cakes are cold, you can get on with the icing. I use a processor just because it makes life easier: you don't need to sieve the icing sugar. So: put the icing sugar, cocoa and Horlicks in the processor and blitz to remove all lumps. Add the butter and process again. Stop, scrape down, and start again, pouring the boiling water down the funnel with the motor running until you have a smooth buttercream.
Sandwich the cold sponges with half of the buttercream, and then ice the top with what is left, creating a swirly pattern rather than a smooth surface. Stud the outside edge, about 1cm in, with a ring of Maltesers or use them to decorate the top in which-ever way pleases you.
Makes 8-10 slices.