It actually looks like it should be a hard cake to make but I promise it isn't. The only thing you do need, is time and a little patients, if you get to excited and peel the collar before it's set it flops or the other side of the coin if you try and wrap before that crucial wrapping time you get a chocolatey mess, but if you leave to long the chocolate is too brittle to wrap.
What you're looking for is that just setting texture to the chocolate, then wrap and pop into the freezer to set completely.
250g caster sugar
250g stork or softened butter
250g S/R flour
1 tbsp vanilla essence
4 large/medium eggs
Mix all of the above in a free standing machine until light and fluffy.
Divide between four 7inch greased sandwich tins (I used Dr Oketer)
Bake in a preheated oven @170 for about 18-22 minutes until firm when the top is gently pressed
Turn out onto wire racks to cool completely
6 tbsp strawberry jam
800g fresh strawberries, chopped into tiny pieces, saving enough to create a ring around the top
600ml double cream3 tbsp icing sugar
1 tsp vanilla essence
Whip the above together until forming soft peaks, fold through half of the chopped strawberries
To start to build your cake, place a sponge onto the bottom, cover with a layer of the strawberry cream, some strawberries.
On the next sponge cover the underside with strawberry jam then place onto the cream, continue until you have used all 4 sponges, cover the top sponge with the remaining cream and a ring of strawberries, pop into the fridge to chill.
To make your collar
300g Good dark chocolate
In a bowl set over a saucepan of water melt your chocolate.
Cool slightly then pour a little at a time into a piping bag,
I made about 4 parchment ones which I found worked really well, you can find great tutorials on You tube how to make them.
Then snip off the bottom and just let the chocolate fall in lines up and down the paper.
I used to frozen pizza boxes to lay my collar on to chill, as if the kitchens to warm it won't set and my fridge wasn't wide enough to lay it in flat, once the collar starts to set, retrieve your cake and wrap it around gently smoothing into place, pop into the freezer until the chocolate feels snappy, the unpeel the parchment.
I made a 50, by drawing the numbers onto a piece of parchment and leaving to set, then popped them in the middle.