This ‘royal’ Champagne cocktail comes in various guises. The classical version, and my favorite, consists of Champagne mixed with crème de cassis, aka blackberry liqueur. Other versions are made with raspberry or peach liqueur. Whichever you choose, a kir royal is traditionally served in champagne flute, as shown in the photo.
1 bottle chilled Champagne
1 bottle crème de cassis
Measure 1 tbsp. crème de cassis into each glass. Top with champagne.