Preheat the oven to 180°C (fan oven 160°C, 350°F, gas 4). Grease and line a 7cm (2 3/4inch) deep, 12cm (5 inch) round cake tin.
Put the margarine in a mixing bowl, add the caster sugar, eggs and Vanilla Extract. Sift the flour and Baking Powder on top and using an electric whisk on a low speed, gently blend the ingredients together. Increase the mixer speed and whisk for a few more seconds until thick and well mixed.
Spoon into the prepared tin, smooth the top and bake in the oven for 50-55 minutes, until risen to the top of the tin, golden and a skewer inserted into the centre of the cake comes out clean. Cool for 5 minutes then turn on to a wire rack to cool completely.
Carefully slice the cake into half. Using the ribbon nozzle, pipe Easy Swirl Icing in a single layer over one of the cake halves and place on a serving plate. Open the pouch and squeeze out half of the caramel Surprise Inside Cupcake Centres. Gently spread the caramel to the edge of the cake if necessary.
Place the other cake half on top and push down gently to sandwich the 2 halves together. Pipe a thick band of Easy Swirl round the edge of the cake and sprinkle with Pink Crystals. Squeeze the remaining caramel into the centre of the cake, and pile the Marshmallows on top. Your cake is now ready to present to your Mum.