1. Using cake such as madeira or Victoria sponge, rub between your hands to form breadcrumb-like cake crumbs.
2. In a clean bowl, whisk together the butter and caster sugar until the mixture becomes light and fluffy and pale in color.
3. Using a wooden spoon, stir in the dark rum (put in around 4 teaspoons – enough to taste – but you can add more or less if you wish).
4. Mix in the ground almonds and sift in the cocoa powder and mix well together.
5. Mix in the cake crumbs to form a firm paste.
6. Take a small amount of mixture (about the size of a walnut) and roll it between your hands to form a small ball shape.
7. Then, place it into the dish of grated chocolate and roll around to give a good coating of grated chocolate.
8. Roll the ball gently between your hands again to reshape the truffle and place it on a clean plate.
9. Once all the chocolate truffles have been made put them in the fridge for about 30 minutes to firm slightly.
10. Remove the chocolate truffles from the fridge and dust with a touch of icing sugar.
11. Place each chocolate truffle in a petit four case before serving.