...until the beer has reduced to make a thick and tasty sauce. At the same time the meat will have become very well cooked tender.
Remarks
For the beer, I advise you to use a dark beer which will give stronger flavour.
In the so-called "Flemish" carbonnade, a little brown sugar or a slice of gingerbread spread with mustard is added to the dish. But, I don't feel that either is necessary.