I tried this in honour of the excellent Aperol Sour my wife and I used to have sometimes at Sorso, the cocktail bar at the Ritz-Carlton in Abu Dhabi. We both enjoyed this and will make it our go-to as a replacement, although this recipe could use a little editing! 30ml of orange bitters? A 15-minute shake (or "share")? Also, 30ml of egg white is more than is needed, in my opinion - 10ml or 15ml usually suffices. Ignoring those elements, a very tasty drink.