I used a mixing bowl instead of a cake tin to make the cake as I wanted a rounded dome shape. You could use round cake tins, and stack two cakes on top of each other.

line the mixing bowl: Fold a piece of baking paper over and over to form a long thing triangle. Hold the point of the triangle at the middle of the bowl, measure to the edge of the bold and trim the triangle to this length.

Open out the triangle, it will now be a rough circle. Cut down one of the lines to the centre point

You should now be able to push the baking paper down into the bowl, you can use the creases to fold the baking paper to fit

Prepare the chocolate cake batter: I used 2x Countdown 450g chocolate cake baking mixes to make my batter

Pour into the lined bowl or cake tins

Bake as per the cake batter instructions. If you are using a large mixing bowl as I did, the cooking time may be longer than in a regular cake tin.

Start with softened butter (not melted, but soft). Use an electric beater or cake mixer to beat the butter until it is as white as possible.

Then add ⅓ of the icing sugar and beat, add ⅓ of the milk, alternate adding the icing sugar and milk until it has all been added, flavour the icing with the vanilla

The buttercream will be used throughout the recipe

Remove the legs from the doll this will become your mermaid cake topper

Use a cake leveler to first level your cake and then split the cake into 4 layers. You could also just use a bread knife. If you are using a bread knife it can be easier to cut the cake if chilled and/or frozen. It would also be ok to do fewer layers. It's up to you

Keep any offcuts of cake you end up with when leveling the cake, as you will use these cake crumbs to form the tail

Take ¼ of the uncoloured buttercream mix in sprinkles to make it funfetti buttercream. (you can use as many or as few sprinkles as you like)

Use the funfetti buttercream to fill the layers of the cake

Crumb coat: Take another ¼ of the uncoloured buttercream and apply a thin layer of it all over the cake. This is the crumb coat, it will make it easier to frost the cake later when you are applying the coloured buttercream. The crumb coat does not need to be perfect

If you have any leftover buttercream save it as you can use it later to form the mermaid tail

Use a small knife or spoon to cut a well out of the top of the cake that will fit the base of the doll. (photo 6)

Refrigerate the cake until the crumb coat is firm. I often do this overnight, but an hour or so will work too.

Colour the buttercream: You should have ½ of the buttercream remaining.  Use a little blue food colouring to colour the icing a pale blue. 

Remove ½ of the light blue buttercream and apply it to the top half of the cake, this can be done roughly

Add more blue food colouring to the remaining buttercream to make a darker blue colour

Apply the darker blue buttercream to the bottom half of the cake

Dip a bread and butter knife (or metal cake spatula) in hot water, shake to remove excess water Use the hot knife to smooth the buttercream, you will end up with an ombré  effect

If you have any leftover buttercream save it as you can use it later to form the mermaid tail

Place the lollypops in a plastic bag. Use a rolling pin to break up the lollypops. I smashed around  12 lollypops, but I probably only needed half this quantity. 

With your fingers, press the broken lolly pops around the bottom of the cake, this is meant to look like colourful coral and seaweed

Create the mermaid

Take the offcuts you saved when leveling the cake, crumble them with your fingers so that you end up with cake crumbs.

Mix these cake crumbs with a little leftover buttercream

The crumb buttercream mix should be easy to work with, use your hands to form a mermaid tail shape.

Position the tail on top of the cake in front of the well you created for the mermaid cake topper.

Frost the tail with a thin layer of buttercream, just enough to hold the candy decorations in place (you can use any colour)

Arrange the smarties or m&ms to look like scales and completely cover the tail. I used pink and purple smarties but you could use any colour combination that you want

Take 2 jubes and position these at the end of the tail to look like flippers, you could also use spearmint leaves for this

Position the doll in the well, you may need to fill in any gaps with a little buttercream and candies.

Your mermaid cake is now complete!