Put the malt vinegar, coriander seeds and a pinch of salt in a large preserving pan and bring to a boil. Add the cauliflower and onion and simmer for five minutes, or until slightly softened but still crunchy.
Meanwhile, put the mustard, flour, turmeric and ginger in a small bowl and gradually whisk in the cider vinegar until smooth. Set aside.
Add the green beans, garlic and sugar to the pan and stir over the heat for 2–3 minutes, or until the sugar has dissolved. Drain over a large bowl to collect the vinegar.
Put the mustard mixture and the vinegar back into the pan and bring to the boil. Reduce the heat and simmer for 10 minutes, or until thick enough to coat the back of the spoon, adding more salt to taste.
Return the drained vegetables to the pan and add more sugar and water if necessary and then take off the heat.
Spoon into hot sterilised jars, seal and cool.
Store for three months in a cool, dark place before eating.