Crush the Digestive biscuits into fine crumbs. Mix with melted butter and milk. Press firmly into a 20 cm pan and refrigerate.
Beat mascarpone, powdered sugar, heavy whipping cream, and hazelnut spread until thick and firm.
Fold in the finely chopped Giotto balls.
Spread the filling over the crust and refrigerate for 1 hour.
Gently melt the hazelnut spread (double boiler), pour over the cake, and refrigerate for 2 hours.
Decorate as desired (whipped cream, Giotto balls, chopped hazelnuts), slice, and serve cold.