Put a martini glass or coupe glass in the freezer for 10 minutes to chill.
Put the raspberries, sugar and lemon juice in a glass and let them macerate for 10 minutes. Muddle with a spoon and then sieve the pulp to extract the raspberry syrup, pressing on the berries with the back of a spoon.
Add the gin, raspberry syrup, egg white and grenadine into a cocktail shaker. Shake hard for 30 seconds.
Add plenty of ice and then shake the cocktail again to froth up the egg white.
Strain into the chilled glass and garnish with a mint leaf and a fresh raspberry.