Place the mustard seeds, vinegar and wine in a bowl. Cover with cling film and leave the mustard seed to soak for a few hours, ideally overnight.
Toast the chopped nuts over a medium heat. In a blender/food processor, puree the nuts with the mustard mixture, sugar and salt for 2-3 mins. until smooth. If the consistency is too thick, add a little water.
Fill the jars
Transfer the mustard to clean preserving jars or jars with screw-top lids that have been rinsed first with hot water, seal the jars immediately.
The mustard tastes best approx. 1 week after it is made, when all the flavours have had time to develop.