- Melt chocolate bar and for butter icing,
- Whisk egg with sugar to form pale and thick mixture. Fold in flour and cocoa powder. Take a greased and lined 9X13 inches swiss roll pan and fill it up with final mixture.
- Bake now on 425*F preheated oven for 12 minutes, place out and turn onto a greaseproof sheet paper lightly dusted with sugar while it is still warm, roll the cake up from one of its short ends. Let cool.
- Unroll the swiss roll and spread with butter icing now re roll. Cut off a piece from one end almost 4 inches long, dip both pieces in melted chocolate. Arrange biscuit on one end of large piece and let set for few minutes.
- On end, turn the smaller piece up and arrange on other end of the large piece of cake. Decorate the candies to resemble with wheels and a funnel and use more sweets with cotton wool to form smoke passing from funnel.