Boil the 280 g sugar until thick, add the finely chopped walnuts, and cook for one minute over a water bath, stirring constantly.
Let cool, then beat in the whole egg and the 8 egg yolks until well fluffy.
Whisk the 5 egg whites to stiff peaks and gently fold into the mixture.
Bake in three layers in a buttered cake tin, about 15 minutes per layer at 180°C.
For the filling, cook the finely ground walnuts together with the caramelized sugar syrup and a little lemon juice.
Brush the cooled layers with apricot jam, then sandwich together with the walnut filling.
For the coating, cook the 8 egg whites with the finely crushed sugar over a water bath, stirring constantly, into a stiff meringue, about 10-15 minutes.
Fold in the finely ground walnuts and a little vanilla.
Coat the whole cake with the meringue mixture, mound it up, and dry it in a low oven (about 100°C) until a thin, crisp crust forms.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.