To a cocktail shaker without ice, add gin, dry vermouth, lemon juice, lemon juice, raspberry syrup and egg white.
Shake well for 30 seconds. Add ice and shake again for 30 seconds. Shake vigorously to aggravate the egg white and get the best layer of foam on top.
Strain into a coupe glass.
Garnish with three raspberries on a cocktail pick.
Notes
Instead of raspberry syrup, you can muddle 3 or 4 fresh raspberries with ½ ounce simple syrup or 1 tablespoon of sugar. Adapted from The Essential Bar Book by Jennifer Fiedler