This is an excerpt from Forme of Cury
(England, 1390)
The original source can be found at
the Project Gutenberg website
MUSKELS IN BREWET. XX.VI. II. Take muskels, pyke hem, seeþ hem with the owne broth, make a lyour of crustes & vynegur do in oynouns mynced. & cast the muskels þerto & seeþ it. & do þerto powdour with a lytel salt & safron the samewise make of oysters.
Other versions of this recipe:
Muskelys in bruette (Two Fifteenth-Century Cookery-Books)
Muskels in bruet (Fourme of Curye [Rylands MS 7])