Burnt Brown Crunchy Bits
The favorite food of His Grace, the Duke of Ankh, these remembrances of meals past found their highest expression in the fryers at Harga's House Of Ribs. His Grace was very annoyed when Sham Harga cleaned out the chippers before a coronation celebration. Burnt Brown Crunchy Bits, fat, starch and sugar are the four major food groups according to many men in Ankh-Morpork.
On a far larger scale, BCB's are a constituent of the legendary fat strata in Überwald, where the Fifth Elephant finally came to its graveyard many aeons ago. Here the term relates to entire mammoths, bison, bears, elk, etc. that were flame-grilled by the impact of the elephant.
Annotation
This is a pun on "Burnt Ends" a favorite at many BBQ locations, it is the burnt and crispy bits from the end of a smoked beef brisket. When mixed with bits of unburnt brisket these burnt brown crunchy bits make a delicious Burnt End Sandwich.