In a bowl, combine the ricotta with the icing sugar, chocolate chips and grated lemon peel, until you obtain a smooth mixture. Finely chop the Cantucci in the food processor, then put the resulting crumbs on a plate. Shape the ricotta mixture into little balls measuring 4-5 cm and roll them in the chopped Cantucci. Put the ricotta balls on a serving dish, cover with cling film and leave to rest in the freezer for 20 minutes. In the meanwhile, in a small bowl, carefully combine the Viallella with the cream. Then serve the ricotta balls accompanied by the chocolatey Viallella sauce.