This is later but another variant.
from A Proper newe Booke of Cokerye
(England, mid-16th c.)
The original source can be found at Thomas Gloning's website or medievalcookery.com
To frye Beanes. Take youre Beanes and boyle them and putte them into a fryinge panne with a dyssche of butter, and one or two onions, and so lette them frye tyll they be browne altogether, then caste a lyttle salte upon them, and then serve them forthe.