You need 2 liters good quality vanilla ice cream. It needs to be the good stuff so that it survives being melted and refrozen ok.
Lots of different chocolates, the best are Cherry ripe, Honey comb and some choc chips. 1 of each bar.
A bag of marshmallows
Pull the ice cream out of the freezer and chop up all the chocolate and marshmallows into little pieces. About 1cm squared but it's better rough.
The ice cream will be just starting to soften now so add the chopped up chocolate and marshmallows in a big bowl and mix it all together. Do it quickly so that it doesn't start to go liquid, just soft.
Line another bowl with plastic wrap and pour in the mixture, press it down and cover. Put back into the freezer at least over night.
When your ready to eat, chill a plate in the freezer and then upend the ice cream pudding onto the plate. If it sticks just run the outside of the bowl under hot water for a few seconds. Remove the plastic wrap.
Chop the pudding into segments and enjoy.