RECIPE (from the BestRecipes.com.au website, slightly altered)
1 x 600g box of vanilla cake mix (I used Betty Crocker vanilla cake)
1 x 85g packet strawberry jelly
1 punnet strawberries, pureed
4 large eggs
120 ml vegetable oil
1/4 cup water
1 tsp strawberry extract/essence
ICING
3 level Tblsp margarine
500 g icing sugar
1 tsp strawberry extract
1 tsp vanilla extract
a few drops of milk to smoothen the consistency of the icing
METHOD
Preheat oven to 180 degrees Celcius (mine is non fanforced gas oven). Line and grease a 12 cup capacity dolly varden cake tin.
Beat eggs in a large bowl till light and fluffy, then add cake mix, jelly crystals, pureed strawberries oil and water (I also added 3 extra tablespoons of maragarine to my batter, but you can omit this if you like).
Beat on medium speed untill all ingredients are combined (don't overbeat). Pour into cake pan (about 2/3 up from the rim)
Bake for 63 minutes (they said 45 min, but it wasn't enough time) or until a skewer inserted comes out clean.
Let the cake cool in the pan and then remove and refrigerate (give mudcake texture if you do this). The next day remove from fridge and let it come back to room temperature. The cake produces a lovely moist almost mudcake/banana bread like texture but not as stable as mudcake. I personally wouldn't use this cake if I was to make a novelty cake, which requeres a lot of cutting and shaping.
ICING
For the icing, combine butter, icing sugar and milk and beat on medium speed until the frosting is light and fluffy and pale in colour (almost white). Add colouring and strawberry & vanilla flavouring.
Place some icing on the bottom of the cake and secure to your cakeboard/serving plate. Ice the cake and quickly sprinkle soft brown sugar to represent the sand. If you wait till the frosting is dry/set, the brown sugar will fall off, so make sure the icing is still wet when you sprinkle the brown sugar. Now you can add your cake topper and water effect (I normaly use blue tinted Royal icing) and shark fins.
The mermaid is then left to dry completely, in this case two weeks, modelling paste dries much quicker and becomes much harder when dried.
Once the mermaid was dry I placed her on the cake and added her fins (green tinted fondant) and hair. For her hair I tinted some fondant brown and used a clay extruder to make her hair. I then added her hair a section at a time (begining at the back of the head, so she wouldn't end up bald!) using sugar glue to stick it down. The reason I did this after she was placed on the cake was so that her hair wouldn't break if I tried to move her, ditto with her fins on her tail.