Drain lychee syrup into a small pan. Cut lemongrass into thirds and bruise with the back of a chef’s knife. Add lemongrass to lychee syrup and bring to a boil over medium-high heat. Reduce heat and simmer for two minutes. Remove from heat and cool to room temperature. Strain and store in refrigerator until ready to use.
Puree lychees in a blender or food processor add in the strained lemongrass-lychee syrup and blend a few seconds more.
Fill a third of a champagne flute with puree mixture and top off with champagne. Garnish with a small strawberry.