This is an excerpt from Le Menagier de Paris
(France, 1393 - Janet Hinson, trans.)
The original source can be found at
David Friedman's website
JANCE is made in this manner: take almonds, put in hot water, peel, grind, and also two pieces of ginger; or put in powdered spices, a little garlic, and untoasted white bread, slightly more of that than the almonds, soaked in white verjuice and a quarter of white wine: strain, then make it boil very well, and serve in bowls. And one should serve it more than other sauces.
Other versions of this recipe:
A Jance (Du fait de cuisine)
Jance Sauce (Du fait de cuisine)