Muddle 2 sprigs of mint with the vermouth and absinthe. Add the gin. Shake with ice and strain into a chilled cocktail glass. Garnish with stuffed olive and remaining mint sprig.
The Savoy has this as 2/3 gin, 1/3 Gancia Sweet vermouth, 1 dash absinthe, 2 sprigs mint, shaken and strained with an olive garnish.