According to the Guardian, a cookbook dating from 1390 owned by the University of Manchester's John Rylands University Library will be digitized and available for perusal on the Internet. It's written in Middle English and is a compilation of recipes by the master cooks of King Richard II's court (that would be the British king who exiled Hotspur, but was then overthrown by said Hotspur, who crowned himself Henry IV in a truly Machiavellian kind of way, and sent Richard II to the Tower. According to Shakespeare.)
Entitled Forme of Cury, the Guardian writes that "it contains the instructions for creating long-forgotten dishes such as blank mang (a sweet dish of meat, milk, sugar and almonds), mortrews (ground and spiced pork), and the original quiche, known in 14th century kitchens as custard."
Hopefully the university will also provide a translation.