I would add "Catalan" as you won't find bull outside Catalonia.
Black or white 'bull' Catalan sausage from Alt Urgell".
From TERMCAT:
ca bull blanc i bull negre
es bull blanc y bull negre (tipo de butifarras catalanas)
fr bull blanc et bull negre (sorte de boudins catalans)
it bull bianco e bull negre (tipi di insaccati catalani)
en bull blanc and bull negre (kind of Catalan sausages)
de Bull blanc und Bull negre (katalanische Wurstsorten)
As for the llardons, it's not a typical ingredient of sandwiches, but I would say it doesn't have the skin. How about "with its own suet"?
http://www.gastroteca.cat/ca/fitxa-productes/llardons_de_por...