This recipe taken from Forme of Curye, ab. 1390 A.D. (Pages 76v & 77r). The images are from the original manuscript as digitized by the John Rylands University Library and the 1780 printing edited by Samuel Pegge.
Tart in Ember Day
Take and parboil onions and herbs and press out the water and chop them small, take bread and pound it in a mortar and temper it with egg, do thereto butter, saffron and slat and raisins Corinth and a little sugar with fine powder and bake it in a shell and serve it forth.
Bring pot of water to boil. Peel and quarter onions, place in boiling water for 2-3 minutes, then drain. Chop onions and parsley and combine with bread crumbs, eggs, butter, currants, sugar, salt, and spices. Pour into prepared pie crust and bake at 350°F for 30-40 minutes, ensuring that the egg is set. Let cool for 10-15 minutes before cutting into serving sizes.