Shake. strain, up.
Ensslin's recipe is 2 parts London Dry gin, 1 part lemon juice, 2 dashes each Maraschino and Creme de Violette, with no garnish. Ted Haigh, in Vintage Spirits and Forgotten Cocktails has this as 2 1/2 oz gin, 3/4 oz lemon juice, and 2 or 3 dashes of Maraschino - it omits the creme de violette, which is a transcription error from Ensslin to the Savoy Cocktail Book. This can be made more floral with more violette and sweeter by reducing the lemon juice.
Recipes for Mixed Drinks, Hugo Ensslin, pg. 7