Start by making the cake. You'll need to make this in advance so that it has plenty of time to cool before icing.

Preheat your oven to 190°C (Gas mark 5/375°F).  Grease the two savarin tins really well with butter or oil (I used spray oil to thoroughly coat mine).

In a large bowl, whisk together the butter and sugar. Add the eight eggs, two at a time, whisking after you add each pair.

Once the eggs have all been whisked in, add the flour, baking powder, 100ml  of the milk and vanilla. Whisk again until fully combined.

Place half of the cake mixture in a separate bowl. Add green food colouring to this bowl and whisk, just until the cake mixture is evenly coloured.

Add cocoa powder and the remaining 30ml milk to the other bowl. Whisk until fully combined.

Using two spoons, divide the cake mixture between the two greased tins, dropping alternate spoonfuls of each flavour into each tin. Once all of the mixture is in the tins, swirl around each tin a couple of times with a skewer to give a marbled effect.

Gently smooth the tops down with a spatula, then pop both cakes in the oven and bake for around 30 minutes.

Check that the cakes are cooked by pushing a skewer into the thickest part of the cake - once cooked the skewer should come out clean when removed from the cake. You may need a bit more or a bit less time depending on your oven.

Once the cakes are cooked, remove from the oven and leave in the pans for ½ hour to cool. This will help you to remove the cakes without sticking.  After ½ hour, run a knife around the edge of each cake, then carefully tip each cake out onto a cooling rack. It should just pop straight out.

Leave to cool completely before icing.

While the cake is cooking, prepare the coconut 'grass'. Place 75g desiccated coconut in a bowl and add green food colouring. If you use gel colouring, you may need to add a little water to help it coat the coconut. Stir well until all of the coconut is coloured, then tip out onto a tray or plate and leave to dry.

Also while the cake is cooking, prepare the marshmallow 'scales'. First separate the marshmallows into colours and then roll them flat.  I found that the quickest way to do this is to place the marshmallows in lines on your work surface and roll them flat with a rolling pin, one line at a time. If you don't put them in lines and just try to roll them at random, you'll run the risk of them all sticking together! Collect all of the flat marshmallow scales in two small bowls and cover until ready to use.

Shape the tail into a triangle by cutting away a slice from the other side, then shape one of the discarded cake quarters into a head.

Put the two cakes together to form an S shape (mine was a backwards S) and check that the whole cake will fit on the board you want to use.

Starting from the tail end, spread buttercream over cake. I did mine in small sections so that the buttercream didn't dry out in between.

Once you have covered the first section in buttercream, start adding the scales. Starting at the base of the tail, push the flattened marshmallows into the buttercream, alternating the colours in overlapping rows.

Follow the shape of the cake as you go around, you'll find the rows will sometimes curve in different directions as you go around the corners!

Make the features; roll 2 white mini marshmallows flat and cut into ovals for the eyes, draw on the pupils with an edible marker pen (or paint them on with food colouring if you don't have one) and roll out a small piece of red fondant, cutting it into a tongue shape.

Attach the features to the head, pushing them gently into the buttercream to hold them in place.