Prepare an 8 inch round/square cake tin by completely lining with cling film (so that it hangs over the sides) and on top of this, base-line with non-stick baking paper.
Place the butter, dark chocolate, golden syrup and cocoa powder into a large, microwaveable/heatproof bowl.
Microwave on medium heat at 30 second bursts stirring between each, to melt all the ingredients until completely blended and smooth (if you don’t have a microwave, you can heat in a saucepan over a low heat, stirring frequently).
Set aside and allow to cool slightly.
Whilst cooling, prepare your biscuits, by either breaking with your hands or bashing (in a clean food bag and using a rolling pin) into smallish pieces. Alternatively, you can cut into thin sticks with a sharp knife. Set aside.
Cut your mini Creme Eggs into halves lengthways.
In a large bowl, mix together the chocolate mixture, biscuit pieces, 150g halved creme eggs and vanilla extract.
Tip the mixture into the cake tin and push to the sides, so that it is evenly spread. It will look quite lumpy on the surface, but that will be covered by the decoration.
Place in the fridge for a couple of hours until fully set.
To decorate :
Remove the fridge cake from the tin and peel off the clingfilm and baking paper. Place on a serving plate.
Melt your white chocolate in a small microwavable (I use glass) bowl, on medium heat at 30 second bursts, stirring between each until just melted and smooth (or place the bowl over a saucepan of just-simmering water, stirring frequently).
Use a spoon to drizzle about half the chocolate over the top of the biscuit cake.
Add a little yellow/orange food colouring paste to the remaining chocolate and mix thoroughly, then drizzle this over the cake as well.
Whilst the chocolate is still unset, top with mini Creme Egg halves and a sprinkle of grated dark chocolate.
Leave to set in the fridge.
* Note: nutritional information is an estimate & may vary according to portion size/ingredient variants.