Make a mixture of the crumbled biscuits and walnuts. Mix with the softened butter and form a layer in a cheesecake form or other similar container. Put it in the fridge for 1 hour.
In the meantime, take the jam out to loosen up at room temperature. Beat it as well. Then scoop from the jam with a small spoon and distribute it carefully on top of the cream.
The important thing here is not to mix the 2 layers but even if this does happen in some areas, don't worry. After you arrange the washed and dried fruits on top, any little mistakes will no longer be visible.
Put thus prepared cheesecake in the fridge overnight. The next day, cut it with a sharp knife into pieces and serve.