Norwegian cold rhubarb soup with mint

1. Remove the leaves of the mint sprigs. 2. Peel the rhubarb and cut it into thin slices. Place the rhubarb peel in a medium saucepan with the water, vanilla bean, sugar, the lemon juice and the leftover stalks of mint (minus the leaves). Bring to a boil, reduce heat and let simmer for 10 minutes. 3. Strain reserving the liquid. Discard the vanilla and mint stalks. To the liquid add the rhubarb slices. Bring it to a boil, take off the heat and leave to cool. 4. Cut the mint leaves into thin strips. Puree the soup in a food processor or blender until smooth. Put in refrigerator to cool completely. 5. Serve the soup ice cold garnished with the strips of mint.