For the crème de vanilla de bourbon, soak the gelatine leaves in a bowl of cold water for 4-5 minutes. Squeeze dry and set aside.
Slowly bring the cream, sugar, vanilla pods and seeds to the boil in a small pan. Remove from the heat and discard the vanilla pods.
Stir the soaked, drained gelatine leaves into the cream mixture until melted.
Strain the mixture through a fine sieve, reserving the strained liquid. Set aside to cool and set slightly, then pour the cooled mixture into four 100ml/3½fl oz dariole moulds and chill in the fridge for three hours, or until completely set.
Meanwhile, for the blood orange sorbet, place the sugar into a pan and dissolve it in the water. Bring the sugar and water mixture to the boil, stirring continuously, then reduce the heat to a simmer and continue to cook for a further 2-3 minutes. Remove from the heat and set aside until completely cooled.
In a large mixing bowl, stir together the blood orange juice and orange liqueur, if using.
Stir in the cooled sugar syrup a spoonful at a time, tasting after each addition, until the orange juice is sweet enough for your taste.
Pour the mixture into an ice-cream machine and churn until smooth and set. Transfer to a plastic container, cover and freeze until needed.
For the poached rhubarb, gently heat the sugar and the two tablespoons of water until the sugar has dissolved. Add the rhubarb and ginger and simmer gently for 4-5 minutes, or until just softened. Strain the rhubarb and set aside to cool. (You can use the drained liquid in another dish, or drizzle it over the finished dessert.)
To serve, turn the crème de vanilla de bourbons out onto four chilled serving plates. Place a scoop of blood orange sorbet and a spoonful of poached rhubarb alongside each.