In a saucepan, combine the rhubarb, blueberries, and rapadura. Simmer for a few minutes, then add the water and a few splashes of sherry. Continue to simmer until the berries begin to release their juices.

Remove the berry syrup from heat and allow to cool. Prep the kale by washing and tearing into small pieces.

Pour the syrup over the kale and toss to coat. Sprinkle the walnuts on top. Cover the salad and let it chill thoroughly in the refrigerator.