Put the stock in a large saucepan and whisk in the raft thoroughly. Heat very gently, Stir from time to time to stop the solids from sticking and burning. As the stock comes to a simmer the raft will begin to coagulate and rise to the surface. At this point you do not need to stir anymore. Turn heat down to a simmer. Once it has set on the surface, make a little hole in it to allow the steam to escape. Simmer very gently for 20 minutes then remove from the heat. Do not boil after the raft is set.
When cool, carefully ladle the consommé through a sieve double-lined with muslin. Taste and adjust the seasoning then add the Madeira and Armagnac. Serve immediately or transfer to a container with a tight-fitting lid and refrigerate. The consommé will keep in a sealed container in the refrigerator for 3–4 days or up to 3 months in the freezer.