Cider Vinegar Mustard
This company is reputed to be the last producing mustard in the Normandy countryside in the traditional way. Records show the method being used back in 1783, and it is undoubtedly older than that. It is a simple blend of mustard seeds, water, organic cider vinegar and salt. Nothing more.
Their mustard is superb - very strong, but likely to mellow if kept out of the fridge.