Prepare the cream according to package directions with the milk and sugar.
I used Irish cream, a very pleasant cream that tastes like Bailey's. The amounts of milk and sugar depend on the type of cream you're going to be using.
Break the cake layer into pieces. Stir the jam and distribute it along the bottom of a cake form, with spaces between each spoonful.
Pour half of the cooled cream on top, put the pieces of cake layer and pour on the remaining cream.
Put it in the fridge for 24 hours to harden, then invert onto a cake platter.