Clean head, removing snout and reserving tongue and brains. Scrub well and place in large kettle. Cover with water; add onion, stuck with cloves, and tongue. Tie celery, parsley, carrot, bay leaf and peppercorns in cheesecloth and drop into kettle. Add salt.
Bring to boil, skim carefully and simmer slowly about 4 hours, or until meat is tender and falls easily from bones. Remove tongue from water after it has cooked 1½ hours.
Lift head onto a large platter. Strain and reserve liquid in kettle. Remove all rind from head; cut the meat and tongue, skin removed and excess tissue from root end, trimmed, into tiny pieces. (Some women like to put meat through food chopper.) Place in large bowl.
Drop brains into a little of the cooking liquid; simmer, covered, 15 minutes. Remove, drain and add to meat and tongue. Season lightly with cayenne, sage and nutmeg. Toss to mix well.
Pack mixture into 9 X 5 X 3″ loaf pan or mold, pressing firmly. Pour ½c. cooking liquid, cooled until lukewarm, over mixture. Cover pan or mold and put weight on it. Chill at least 48 hours before using. Slice to serve.