Grandmas Walnut Cake

This recipe is indeed by my Grandmother...

Ingredients:

For the Cake:
3 layers of sponge mixture
½ jar blackberry jam
400g Walnuts
200g icing sugar
300g heavy sour cream

For the gloss:
1 fresh egg white
Juice of ¼ Lemon
200g icing sugar

Instructions:
Finely chop the Walnuts and mix with the icing sugar and the cream. Put the first sponge on a plate and coat the top of it with half of the Walnut mass. Now you coat it with more than 1/3 of the jam. Put the second sponge on top of it and repeat the procedure. Than put the third layer on top and coat it with the rest of the jam.

For the gloss whisk the egg a bit and mix with icing sugar and lemon juice. Coat the whole tart with it.