My sister replicated a recipe of mine (http://theyearinfood.com/2011/03/mussels-and-fennel-in-ale.html), which I made without a hitch. When she added cream to the broth, which is composed mostly of Belgian ale, it curdled. Any thoughts? My instructions said to turn off the heat before adding the cream, which she forgot to do. Could it be that? Could it be the type of beer used (perhaps a beer with more acid would cause this)? Cream vs. half and half? She's asked my advice and I'm at a loss.