Green’s Dictionary of Slang

cock (a Broseley) v.2

[17C SE cock, to place a match in the cock of a matchlock gun]

to smoke.

[UK]G.W.M. Reynolds Mysteries of London I 399: The king had in the meantime amused himself with what, in bis own lingo, he termed ‘cocking a broseley’* [note] *Smoking a pipe.
[UK]Hotten Sl. Dict. 103: COCK, a smoking term; ‘cocking a Brosely,’ i.e., smoking a pipe. Brosely in Staffordshire is famous for ‘churchwardens.’.
[UK]Farmer & Henley Sl. and Its Analogues.