Tangy rhubarb soup and soft dollops of fresh mint ice milk sing of spring with each spoonful.
Stir together rhubarb and granulated sugar; set aside. Tie together lemongrass stalk and mint with kitchen twine to form a bundle; set aside.
Bring wine to a boil in a medium saucepan; cook until reduced to 2 cups, about 10 minutes. Remove from heat.
Whisk together confectioners' sugar and cornstarch. Whisk in 2 tablespoons water. Whisking reduced wine, add cornstarch mixture. Stir in rhubarb mixture.
Bring wine mixture to a boil. Add lemongrass-mint bundle. Remove from heat; let cool completely. Refrigerate until cold, at least 1 hour (or overnight).
Discard bundle. Divide soup among 4 chilled bowls. Dip 2 tablespoons in hot water, and use them to form 4 scoops of ice milk. Place 1 scoop in each bowl.
