How to Make the High Fashion Cocktail (Common Man Cocktails)

This sounds a bit unique with the sour yet floral elements. Certainly looks well put together.

Recipe
2 oz. Gin
1 1/4 oz. Elderflower Liqueur
1 1/4 oz. Grapefruit Juice
2 Dashes Rhubarb Bitters
Grapefruit Peel Garnish