For the first layer, melt 150g of milk chocolate, pour it into the bottom of the tin and refrigerate for 30 minutes.
Next, make the caramel. Heat up the caster sugar until it begins to caramelise, then add the butter and finally the cream. Allow it to cool before pouring on top of the chocolate (save a little bit), then refrigerate for 30 minutes.
Now make the crispy layer. Melt the 200g milk chocolate, add the leftover caramel then stir in the Rice Krispies and put back in the fridge for 30 minutes.
Add the final layer of chocolate on top, refrigerate for 30 minutes, then remove from the tin and cover the sides with chocolate too!