Add the gin, lemon juice, lime juice, simple syrup, heavy cream, orange flower water and egg white into a shaker and shake without ice for about 10-15 seconds. Add 3 or 4 ice cubes and shake very well and when you are done, shake a little bit longer... and then another round of shaking 10-20 seconds. Double-strain into the prepared collins glass. Now add some soda water to the empty shaker to pick up any egg white left behind and then top off the cocktail to rise up the head of white foam. Enjoy and consider yourself a bartender now ;).