Place 1/4 cup of pineapple, 3-4 mint leaves, 1/2 teaspoon sugar (or simple syrup), 1/2 ounce pineapple juice, and 1/2 ounce of lime juice in the bottom of a Champagne glass.
Using a muddler, crush the pineapple and mint to release the oils. Stir in 1 ounce of rum.
Top with sparkling wine until glass is filled.
Garnish with pineapple, lime and fresh mint leaves, if desired.
Repeat with remaining glasses.