Bring the tropical fruit and lime juices to a boil in a pan and reduce them to approx. 400 ml. Leave 350 ml in the saucepan and pour the remainder into a bowl to cool then chill, covered, for approx. 1 hr.
Add the dissolved agar agar to the juice in the pan and bring to a boil, stirring. Reduce the heat and simmer for approx. 2 mins. Add the passion fruit and mix well. Pour the mixture into the glasses and cool, then cover and chill for approx. 1 hr. or until the mixture is firm.
Add the quark and the icing sugar to the reserved juice in the bowl and mix well. Using a rubber spatula, carefully fold in the whipped cream, spread onto the jelly, cover and chill for approx. 30 mins.
Spear a kumquat on each wooden skewer. Sprinkle pistachios over the dessert and garnish each portion with a kumquat skewer.