For the rhubarb and red currant jelly, first mix the two juices. Then mix the jelling powder with about 2 tablespoons of sugar and add to the juice. Then bring the juice to a boil while stirring.
When the fruit juice comes to a boil, add the remaining sugar and bring to a boil again while stirring. Bring to a boil for about 3 minutes – then remove from heat and stir in the sparkling wine. Pour the still hot rhubarb and red currant fruit jelly into the glasses and seal.