Yellow Pepper Sauce

This tart and spicy sauce is rather curious as it's a pepper sauce made without pepper.

Source [Le Viandier de Taillevent, T. Scully (ed.)]: Poivre jaunet. Broiés gingembre, saffren, pain hallé, et deffaites de vin aigre et faites boullir; et acuns y metent graine et girofle au verjus.

Source [Le Viandier de Taillevent, J. Prescott (trans.)]: Yellow Pepper [Sauce]. Crush ginger, saffron and browned bread, steep in vinegar, and boil. Some cooks add grains of paradise, cloves and verjuice. (BN manuscript, p. 33.)

Source [Le Ménagier de Paris, J. Hinson (trans.)]: YELLOW OR BITTER PEPPER. Take ginger, saffron, then take toasted bread soaked in liquid from the meat (and even better is a little cabbage-water), then boil, and when boiling add the vinegar.