Directions

1. To prepare simple syrup, put rhubarb, agave nectar and water into a heavy saucepan. Bring to a boil. Turn heat to simmer and cook, stirring every so often, until mixture is somewhat reduced and slightly thickened. Remove from heat. Let cool about 30 minutes. Strain mixture through a fine sieve, pressing gently with a spoon to release all the liquid. Let cool completely and pour into a glass container. Rhubarb syrup will keep for a few weeks in the refrigerator. Makes 2 cups 
2. To prepare spritzer, mix wine and rhubarb syrup in a large pitcher. Add a small handful of fresh mint leaves to the pitcher. Use a wooden spoon to gently crush leaves. Stir well. Add seltzer water just before serving.  Serve over ice cubes and garnish with more mint.