The use of a flour-and-water paste to seal the casserole is an old cooking technique that ensures no flavour or moisture is lost.
Carbonnade of Beef: Use beer instead of stout, omit the carrots, pork and allspice, and pour 1 cup beef stock, flavoured with 1/2 teaspoon each of sugar and nutmeg and 1 teaspoon vinegar, over the ingredients before sealing the casserole with the dough. After discarding the dough seal and bag of herbs, cover the top of the casserole with baguette slices spread with Dijon mustard, pushing them down into the gravy. Cook uncovered for a further 30 minutes (the bread will float to the top and form a brown crust).
I have cooked tried similar recipe to this i really enjoy a glass or 2 of stout however it has a rich sugary taste which overdone in cooking spoils a otherwise rich enough dish - 15 Dec 2008
Altered ingredient amounts. 1/2 the stout it's full of sugar and spoils the taste - 15 Dec 2008