Use a channel knife or a vegetable peeler to pare a long, thin strip of lemon peel from a fresh lemon. If you're using a peeler, clean up the edges of the strip with a paring knife.
Twist the lemon peel strip around the handle of a bar spoon or a chopstick. Set it aside while you prepare the drink.
Cocktail
Add the Creme de Cassis to your cocktail glass.
Carefully pour in the Champagne.
If you'd like, give it a gentle stir with a bar spoon so everything mixes together.
If you made a lemon peel garnish, rest it on the edge of the glass, and serve. Cheers!
Notes
If you want to change up the garnish, try some fresh berries! You can add fresh raspberries, or a blackberry, directly to your serving glass.
You can use your favorite sparkling wine if you don't have Champagne. Prosecco and Cava both taste great in this drink!