Combine the lemon juice, sugar, vodka, Limoncello, and vermouth in a large nonreactive bowl and stir until the sugar is completely dissolved. Cover and refrigerate until chilled, 1 to 2 hours. Add the Champagne and stir to combine.
Serve over ice in highball glasses, garnished with lemon twists.
Recipe courtesy Emeril Lagasse
2/3 cup superfine sugar
1 cup vodka
1/2 cup limoncello
2 teaspoons vermouth
1 (750 ml) bottle chilled dry Champagne or sparkling wine
Lemon twists, for garnish