For the base, line a baking dish (21 x 33 cm) with biscuits. Briefly boil water and sugar and mix with raspberry syrup. Soak the biscuits with it.
For the cream, mix mascarpone, yogurt, sugar, vanillin sugar and flavoring. Whip the cream with cream stiffener and fold into the mascarpone mixture. Chill for 2 hours.
For the topping, mix the grits with cake jelly and heat. Remove from heat and smooth over the cream just before it gels.
Sprinkle the grated couverture on top. Cover the mold with plastic wrap and refrigerate preferably overnight.