Place the gin, vermouth, lemon juice, raspberry syrup and egg whites in a cocktail shaker and fill two-thirds full with ice. Cover and shake vigorously for 25 seconds.
Strain the mixture into a glass or small bowl, dump out the ice, and return the mixture to the shaker, cover and shake for 15 to 20 seconds.
Pour into a chilled coupe glass. Garnish with a skewered raspberry or two.