Boil malt vinegar, coriander seeds, and salt in a preserving pan.
Simmer cauliflower and onion for five minutes until slightly softened.
Whisk mustard, flour, turmeric, ginger, and cider vinegar until smooth in a bowl.
Add green beans, garlic, and sugar to the pan and stir until sugar dissolves.
Drain the vegetables over a large bowl to collect the vinegar.
Return the mustard mixture and the collected vinegar to the pan and boil.
Simmer for 10 minutes until thick enough to coat a spoon.
Return vegetables to the pan and add more sugar or water if necessary.
Spoon the mixture into hot sterilised jars, seal, and let cool.