Rinse coupe with Creme de Cacao. Shake all ingredients for 20 seconds (you're looking to have a bit more dilution than normal to bring out the woodyness of the Cassis) except garnish and double strain into coupe. Express long twist of lemon peel and rest across the drink.
1⁄2 oz Maurin Quina
1⁄4 oz Lemon juice
1 twst Lemon peel (Expressed, garnish)