This is the only infor I could find: "Pale, wheat and caramel malts are blended with natural vanilla flavor to provide a rich and creamy body. The result is a refreshing ale with flavors reminiscent of an old-fashioned Creme Soda."
it might be worth contacting the brewer for some tips. Baring that you could just make a pale ale (light on the hops) and add some vanilla extract or vanilla beans to taste.