For the cream:
Beat the sour cream with the lemon juice and rind, honey and powdered sugar in a suitable container. In a separate container, beat the cold confectionery cream to snow and then add it to the cream in the 1st container.
Arrange the 1st layer of biscuits in a tray/form, then smear with cream (about 1 finger width thick) and sprinkle on jam in a jerky motion.
Alternate between biscuits, cream and jam in this order until you've filled the form but be sure to finish off with cream. Put thus prepared cake in a fridge to set, best if overnight.
The next day, before serving, smear generously with blueberry jam, take it out of the form and stick crumbled walnuts along the sides.
Optionally you can decorate it further but the blueberries are plenty eye-catching by themselves.