Beat the butter or margarine with a wooden spoon or mixer until creamy. Slowly add the sugar, together with the vanilla sugar, salt and almond extract, alternating with the eggs. Mix the dough until it is very foamy and the sugar has been thoroughly dissolved. Sift in the flour with the baking powder, add the ground almonds, and mix everything together quickly.
Carefully coat a springform with butter or margarine. Pour the batter in and smooth down the surface. Peel the apples, cut in half lengthwise, and remove the cores. Cut into the outer surface a few times with a knife, but don’t cut all the way through. Brush apples with the lemon juice. Place the apples close together onto the batter, core side down. Soak the currants for a short time in hot water, wash thoroughly and rub dry in a cloth. Sprinkle the currants, together with the slivered almonds over the apples. Bake the cake at 350 degrees for 75-80 minutes or until golden brown. Remove from the oven and let cool before dusting with icing sugar.
Serve with whipped cream.
Note: I always leave out the optional items as I find they don’t they add much to the flavour of the cake.