Put rhubarb, stem ginger, stem ginger syrup, grenadine and sugar into non-stick saucepan
Cook for 4-5 mins, until rhubarb has started to soften
Pour into a shallow tray and leave to cool- chill
Pour cream into bowl and whisk to soft peak stage
In separate bowl, whisk together cream cheese, yogurt, lemon zest, vanilla extract, sugar and orange liqueur
Fold into whisked cream
Crush biscuits with rolling pin, in a plastic bag
Divide crumbs between 2 dishes
Spoon over the creamy cheese mixture
Spoon the chilled rhubarb mixture over the creamy cheese layer