Grate the cleaned apples, add the cinnamon to them, plus 1/2 the coarsely ground walnuts.
Separately, mix the sour cream and sugar, beat with a mixer until the latter melts. Start arranging the cake in a rectangular form or tray as follows:
Layer of biscuits, layer of apple mixture, layer of cream, then biscuits again and so on until out of ingredients. Be sure to finish off with sour cream. Sprinkle on the remaining walnuts on top.
Leave in the fridge for a few hours before serving.