Preheat the oven to 180°C (160°C Fan, Gas Mark 4). Grease and line an 18cm (7inch) square tin and a 900g (2lb) loaf tin. For the bat cake, put 100g (3 ½ oz) margarine, 100g (3 ½ oz) caster sugar and 2 eggs in a mixing bowl. Sieve 100g (3 ½ oz) flour, the cocoa powder and 5ml (1tsp) Baking Powder on top.
Carefully mix all the ingredients together until well blended.
Spoon into the prepared square tin, smooth the top and bake for about 25 minutes until lightly risen and firm to the touch. Leave to cool for 5 minutes then turn on to a wire rack to cool completely.
Put the chocolate cake on a board and using a bat cutter approx. 10 x 4.5 cm (4 x 1 ¾ inch) stamp out 6 bats – you may need to cut out the shapes on the diagonal in order to make 6 bats. Make sure your bat cutter will fit inside the prepared loaf tin. Keep the chocolate cake trimmings for cake pops or truffles. Set aside.
Use the remaining cake ingredients to make up another mixture as above, and flavour with Madagascan Vanilla Extract.
Spoon one third of the mixture into the prepared loaf tin, and spread to cover the base. Arrange the sponge bats, upright, down the length of the tin – they should fit snugly together.
Carefully spoon the remaining cake mixture on top of the bats, smooth the top then gently tap the tin on the work surface to help the mixture settle round the bats and to prevent it bubbling out of the tin during cooking. Make sure the bats are well covered in cake mixture to help create the surprise.
Bake in the oven for 45-50 minutes until lightly risen, golden brown and firm to the touch. Leave to cool for 10 minutes before removing from the tin and cooling on a wire rack.
To decorate, sieve all but 15g (1/2oz) the icing sugar into a bowl with the cocoa. Mix in approx. 30ml (2 tbsp) warm water to make a smooth, soft icing. Spread over the top of the cake, allowing the icing to drizzle down the sides. Leave the icing to set for 30 minutes before proceeding with the final decoration.
Sift the remaining icing sugar into a small bowl and add 30 drops of Neon Orange Gel Food Colour. Mix together with a few drops of warm water to make a pipeable, vibrant orange icing. Spoon the icing into a small uncut piping bag, then cut off the end of the bag to give a narrow piping hole.
Pipe the orange icing diagonally, in a quick back and forward motion, over the chocolate icing to decorate. Leave for a few minutes to set before serving.