Of all the medieval uses for verjus, one of the most important and enduring uses was in mustard making, one of the oldest condiments. The word mustard comes from the Latin words mustum, the unfermented juice of crushed grapes and arden, an adjective for "fiery." It is no stretch of the imagination to concur that Dijon, in the Burgundy region of France became the capitol of mustard making because of its abundance of unripe grapes and wild mustard plants that grow in the vineyards.

Verjus has gone in and out of popular use for as long as man has been writing about food and is for the first time enjoying great popularity in the great restaurants of the United States.

Verjus was a staple in the medieval kitchen. The Viandier of Taillevent, another important archive of early French cooking, French cooking, makes 12 references to verjus. The following recipes have been pulled and translated from various medieval cookbooks.

Ginger and Almond Sauce
Take the quantity of almonds that you need, well blanched, and well ground. And so that they don't turn oily, as has been said before, add a little cold water when pounding. And take a little of the inside of the bread, first soaked in verjuice, and pound it with the said almonds, adding enough white or peeled ginger. And this mixture is to be blended with good verjuice, or orange or lemon juice, according to the tastes of your master or others. And this sauce can accompany all boiled meats on meat — eating days, and in Lent.
(Sent Sovi)

Cameline Sauce
To make the best cameline sauce, take blanched almonds and grind them and sieve them, take dried currants and cinnamon and cloves and a little of the inside of the loaf, and grind all these together and mix with verjuice and it's made.

Mustard
If you wish to provide for keeping mustard a long time do it at wine — harvest in sweet must. And some say that the must should be boiled. Item, if you want to make mustard hastily in a village, grind some mustard — seed in a mortar and soak in vinegar, and inegar, and strain; and if you want to make it ready the sooner, put it in a pot in front of the fire.