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.