In a stainless steel pot, combine the rhubarb, sugar, water, white wine, vanilla bean, and cinnamon stick (do not use a copper, iron, or aluminum pot, as they can be discolored by the strong acidity from the rhubarb and may affect the taste of the soup). Bring to a boil over medium-high heat, reduce the heat to medium-low, and simmer gently for 25 minutes, or until the rhubarb is very soft.
Remove the cinnamon and vanilla and discard the cinnamon. Scrape the remaining seeds out of the vanilla bean with the back of a knife and return them to the soup. Discard the bean. If you want the soup to have a somewhat thicker consistency, add the potato starch and bring to a boil. Remove from the heat. Add half the strawberries to the soup and set aside to cool.
Pour the soup into deep bowls, garnish with the mint, the remaining strawberries, and sour cream, if desired, and serve at room temperature or chilled.