This cocktail is the perfect way to begin a romantic dinner for two: a simple combination of blood orange nectar, St. Germain elderflower liqueur, and Prosecco. Serving it in a coupe is a more elegant, unexpected alternative to a Champagne flute, but a flute would work just as well.
Stir together the orange juice, lemon juice, sugar, and water in a small saucepan over medium heat. Bring to a boil, then lower the heat and simmer for 5 minutes.
Let the nectar cool slightly, then strain it through a fine-mesh strainer into a 1-quart glass jar or another container with a lid. Let cool. Cover and refrigerate for at least a few hours and up to 2 weeks.
Make the cocktail
Combine the blood orange nectar and St. Germain in a cocktail shaker filled with ice and shake.
Pour the Prosecco into 2 chilled coupe glasses or flutes and strain the blood orange-St. Germain mixture into the glasses. Serve!