1/2 cup sugar
1/2 cup water
1 1/2 cups chopped hulled strawberries
6 thin lemon slices
1 750-ml bottle chilled Prosecco
Stir sugar and 1/2 cup water in heavy small saucepan over medium-low heat until sugar dissolves. Increase heat and bring to boil. Cool syrup.
Divide strawberries among six 6- to 8-ounce glasses; add 1 tablespoon syrup to each and mash with muddler or handle of wooden spoon. Add lemon slice to each and mash to release flavor. Add several ice cubes to each glass, then fill with Prosecco.