*Also called orange flower water; available in liquor stores and in the specialty foods section of some supermarkets.
In large cocktail shaker, combine gin, orange blossom water, egg white, half-and-half, lemon juice, lime juice, and simple syrup. Shake vigorously for 25 seconds. Add ice and shake for 30 seconds more.
Strain mixture into 8-ounce glass. Slowly pour soda water down inside edge of shaker to loosen remaining froth. Gently ease soda water/froth mix onto drink and serve.