On large piece of heavy aluminum foil, sprinkle 1/2 package dry onion soup mix. Lay rinsed brisket of beef on this, then sprinkle remaining dry soup onto meat. Shake cooking sherry on top. Seal foil with folds at top and sides to hold juices.

Bake for 2 hours at 350°F and check for tenderness. When done, cool in juice and save juice. Refrigerate meat and juice separately. When chilled, slice meat across the grain. When ready to serve, heat meat, covered, at least 1/2 hour. Warm juices in a separate pan, pouring some over meat when serving and rest on side for gravy.