An infused syrup flavored with rhubarb and ginger adds a hint of pink and a sweet-tangy fillip to sparkling wine. It's not excessively sweet, but you can increase the sugar if you like.
For a fancy serving garnish, finely chop 1 tablespoon of crystallized ginger and then place in a small food processor with 4 tablespoons of sugar. Process until finely ground. Place the ginger sugar on a small plate, run a wedge of lime around the rim of each glass and dip in the sugar. The rhubarb syrup will keep for up to 2 weeks, refrigerated.
Place the rhubarb, ginger, sugar, and water in a small saucepan and bring to a boil over high heat, stirring to dissolve the sugar. Reduce the heat to low and simmer until the rhubarb is very tender, about 15 minutes. Remove the pan from the heat and let stand for 10 minutes.
Place a fine mesh sieve over a small bowl and transfer the mixture to the sieve. Press lightly against the solids to extract the syrup. Don't press too hard or you'll force some of the rhubarb purée through the sieve, which will cloud the syrup. You should have about 1/2 cup. Discard the solids and chill the syrup until cold.
To serve, pour 2 tablespoons of syrup into each glass and top with sparkling wine. Serve cold.