Preheat the oven to 170C/Gas4; grease a giant cupcake tin with sunflower oil
Beat together until combined the flour, sugars, butter and beaten eggs; add the cocoa powder and beat until combined; fold in the yogurt and crushed Maltesers using a large metal spoon
Pour the batter into the prepared tin halves and bake on the middle shelf of the preheated oven for about 1 ½ hours or until a skewer inserted into the middle of the cakes comes out clean; leave to cool in the tin for 10 minutes then turn out onto a wire rack and cool completely
To make the buttercream, beat the butter, icing sugar, drinking chocolate and cocoa powder together until light and fluffy
Sandwich the two cake halves together with a third of the buttercream and the crushed Maltesers; spread a thin layer around the sides of the base of the cake and stick the chocolate fingers; spread the remaining buttercream over the top half of the cake and decorate with the sweets
4 servings