Shards of the ancient cookware, which were at least 6,100 years old, contained residues from plants which resemble those found today in seeds of garlic mustard, a peppery spice.
The spice, part of the mustard family, has little nutritional value but all but one of the pottery fragments also contained residues of more substantial foods such as animal fats and starchy plants.
The findings suggest that the strong-tasting spice was added for flavour rather than nourishment, and contradict the traditional view that hunter-gatherers in the pre-Neolithic and early Neolithic eras cultivated and ate plants primarily for their energy content.
Dr Hayley Saul from the University of York, who led the study, explained: "Until now it has been widely accepted that the calorific content of foods was of primary importance in the decisions by hunter-gatherers about what to eat."
The finding of the plant silica residues, known as phytoliths, similar to garlic mustard and the method used to identify them "open up a new avenue for the investigation of prehistoric cuisines," she added.
The food deposits were identified on pottery shards from three sites in Germany and Denmark, dating to between 6,100 BC and 5750 BC and spanning the period in which hunter-gatherers first began farming.
After comparing the plant silica deposits against those found in 120 modern day European and Asian species, the researchers established that they were most similar to garlic mustard.
All but one of the pottery samples also contained a range of fats from land and marine animals, and starchy plant residues, which would have provided "the bulk of the energy" in the meal, researchers said.
Writing in the PLOS ONE journal, researchers said it was unclear whether the practice of spicing food originated in the western Baltic or was brought there from the Near East.
But they wrote: "It is now established that the habit of enhancing and altering the flavour of calorie rich staples was part of European cuisine as far back as the 7th millennia BC."