Shake, strain, coupe. No garnish.
May be too sweet for modern tastes. Ted Haigh suggests using 1/2 oz or a scant splash of Crème de Cacao. Dan Perrigan suggests a mere 1/2 tsp. Also, consider using Cocchi American rather than modern Lillet.
Also Vintage Spirits & Forgotten Cocktails, Ted Haigh, p272. Dan Perrigan http://egullet.org/p1770015
Cafe Royale Cocktail Book (1937), reproduced in The PDT Cocktail Book