Salt the rim of a cocktail tumbler. 

Muddle the tarragon and maple syrup in a martini shaker until the herb is well muddled and a green syrup has formed. 

Add the vodka and grapefruit juice and some ice. 

Shake, then using the strainer, pour the contents into the salted tumbler over ice. 

Garnish with a grapefruit wedge and a sprig of tarragon.