Beat the confectionery cream with a mixer to a thick cream. Add the sour cream. Beat until homogeneous.
Lay out a sheet of plastic wrap. Arrange 3 columns of 6 biscuits each, firmly next to each other. Smear on a layer of blueberry jam. Arrange a 2nd layer of biscuits on top. Smear generously with cream on top, then place washed and chopped strawberries.
Before cutting it, leave it for 3-4 hours in the fridge to set and for the biscuits to soften.