For the Giotto cake, first prepare the dough. Cream the butter and sugar until light and fluffy. Add the eggs one at a time and mix until the mixture has a creamy consistency. Add hazelnuts, almonds, flour and baking powder and mix to a dough.
Grease a springform pan with butter and pour in the batter. Bake in the preheated oven at 160 °C for about 30 minutes. Allow to cool in the pan, then remove and cut through once.
For the filling, roughly crush the Giotto balls. Whip the cream with the cream stiffener until stiff. Pour some of the cream into a piping bag fitted with a star-shaped nozzle and set aside for the garnish. Stir the crushed Giotto and the cream and spread half of it on the cake base.
Carefully place the second half of the pastry on top and spread the remaining cream all around the cake. Sprinkle the cake with the coarsely chopped hazelnuts.
Using a piping bag, pipe rosettes in a circle on the edge of the Giotto cake and place a Giotto ball on each rosette. Refrigerate until ready to eat.