Place chocolate, butter, milk and sugar in saucepan over a low heat, stir occasionally. Once chocolate and butter has melted remove from heat, stir until fully combined. Allow to cool to room temperature.
Preheat oven to 160°C. Grease 2 x loaf tins and line the base and sides with baking paper.
Once chocolate mixture has fully cooled stir in vanilla and eggs. In a large bowl combine flours together. Stir in a cup of chocolate mixture until it forms a smooth paste. Add another cup of the chocolate mixture and mix thoroughly. Stir in the remaining chocolate until smooth.
Split mixture evenly between tins and bake for approx. 1 hour 30 minutes or until cooked in the centre (when an inserted skewer pulls out clean). Allow to cool on a wire rack. Once cakes have fully cooled, cut into shapes.
Take the first loaf and trim the sides and one end so that they are straight. Trim the remaining end on an angle to form the front of the train.
Take the second loaf and trim the sides so that they are straight and match the width of the first loaf. Cut into two sections to form the train cab (which sits on top of the first loaf) and the trailer (follow our guide picture below). Assemble on a cake board or tray and ice with buttercream icing. Decorate with sweets of your choice.
Beat together butter and icing sugar. Add 40ml milk and the vanilla, beat for five minutes. Carefully add food colouring a drop at a time, mix thoroughly before adding more, until you get the desired colour. Add extra milk if icing is too stiff to spread easily.
Tip: Gel Food Colours work really well and won’t make your icing runny, look for them in specialist cake decorating stores. Dip a clean toothpick into the gel then drag through the icing to deposit the colour. Mix well. Use a clean toothpick to add more colour if desired.