This is an excerpt from Le Viandier de Taillevent
(France, ca. 1380 - James Prescott, trans.)
The original source can be found at
James Prescott's website
Tench. Scalded in water [and cooked]; eaten with Green Sauce. Fried; in pottage. Roasted inside out; powdered with cassia powder and then plunged in vinegar and a bit of oil.