I went over to our local shop for supplies this morning and found chocolate at half price, Cadburys Dairy Milk since you asked. I needed some for Naomi (post operation recovery prescription), so had? to get two 230g bars. This gave me an idea so I also brought a packet of digestive biscuits and a small bar of White Chocolate.
Heres my take on the titular cake bar.
Line a 7 inch square tin with foil and set up a bain-marie to melt the chocolate.
Reduce about 250g of biscuits to crumbs and add butter, mixing until you get a paste (about 200g).
Press this paste evenly into the foiled tray.
Spread the paste thinly with jam
Break half of the white chocolate bar into small chips and scatter over the jam. Put the rest into the melting chocolate.
When the chocolate has melted pour over the cake and spread well..
Put into the fridge to set, about 90 minutes.
When the chocolate has set, cut into squares and enjoy.