3 1/2 teaspoon unflavored gelatin (measured from two 1/4-ounce envelopes)
3/4 teaspoon orange-flower water (optional)
Ingredient info: Orange-flower water, a flavoring extract, is available in the cocktail-mixers or baking section of better supermarkets and at liquor stores and Middle Eastern markets.
Directions
Place raspberries, 1/4 cup sugar, and 1 tablespoon lemon juice in a medium bowl; toss gently to combine. Let stand at room temperature until raspberries release their juices, tossing occasionally, 20-30 minutes.
Place 1/2 cup Prosecco in a small bowl. Sprinkle gelatin over and let stand 5 minutes to soften. Bring 1 cup Prosecco to a boil with remaining 1/2 cup plus 2 tablespoons sugar, stirring until sugar is dissolved. Remove from heat; add gelatin mixture and stir until dissolved.
Transfer gelatin mixture to a large pitcher. Add raspberries with juices, remaining Prosecco, remaining 1 tablespoon lemon juice, and orange-flower water (if using), stirring to dissolve any sugar.
Using a slotted spoon, divide raspberries equally among coupe glasses or other small wide, shallow glasses or cups. Divide Prosecco mixture equally among glasses, about 3/4 cup per glass. Chill gelée until firm, about 3 hours. DO AHEAD: Gelées can be made up to 2 days ahead. Cover and keep chilled.
