Transforming a family-friendly, daily-use condiment like Ketchup, into a fermented food is one of the easiest way to fit fermented foods into mealtimes. Even the pickiest of eaters won’t know the difference!
Mix the tomato paste and honey in a bowl. Whisk in roughly ¼ cup of the Whey with vinegar, salt, allspice, and cloves. Continue blending until all the ingredients are evenly dispersed and the mixture is smooth.
Spoon the homemade ketchup into a glass jar, top with the remaining Whey, and cover with cheesecloth secured with a rubber band or string. Let sit undisturbed at room temperature, out of direct sunlight, for 3 days.
After 3 days, uncover the ketchup and stir it thoroughly. Cover with an airtight lid and transfer to the refrigerator for storage. You can use it immediately, or store it in the refrigerator for several months.