Combine the raspberries, sugar, lemon juice, and orange zest in a saucepan and bring to a boil.
Simmer for about 5 minutes, stirring occasionally.
Puree the sauce in a blender and strain it through a fine sieve.
Refrigerate the sauce until needed.
In a champagne glass place, one tablespoon of sauce and pour in the sparkling wine. Gently stir with the bartender spoon and top with fresh mint.