The rich caramel flavours from the Guinness add special depth to this barbecue sauce. Using the beer as the base means the sauce is neither too sweet nor too vinegary. Like a lot of homemade sauces, it is so much better than any store-bought variety. We all know the Thermomix makes this kind of pot-stirring dish a breeze. You could use a heavy artisan brew in place of the Guinness.