you put the condensed milk in a pot of boiling water (on a hob) and leave simmer on a gentle heat for about two hours (you put the whole can in the water dont open it or anything just buy the condensed milk and put it in the pot, you can remove the label if you want to)
crush the biscuits in the bottom of a cake tin, put the condensed milk(now toffee) on top of the biscuits then add the sliced bananas then finally put the whipped cream on top decorate with whatever you want eg.grated chocolate or crushed Cadbury's Flake refridgerate for about an hour before serving and store in the fridge. it will keep for quite a long time but it will probly go very fast as it is very tasty. forgot to say take out of cake tin after the hour refridgeration and serve on a nice plate or something.