Puree the bananas with sugar and lemon juice. Stir the QimiQ vanilla until smooth, add the mashed bananas and mascarpone and mix well. Finally fold in the whipped cream.
Line a loaf pan with plastic wrap. First pour in a bit of cream, then put in the ladyfingers and pour chocolate sauce on top. Brush with the cream, then repeat the layers until the cream is used up.
Let cool well, at least 4 hours. Turn out onto a serving platter and decorate with chocolate chips.