Wash jars in soapy water and preheat the oven to 140°C.
Dry the jars upside down on a rack for 30 minutes.
Combine vegetables with salt in a non-metallic bowl and sit for 24 hours.
Rinse the vegetables thoroughly in cold water.
Simmer onions in malt vinegar within a large saucepan for 15 minutes.
Whisk 75ml white wine vinegar with mustard, turmeric, ginger, chilli, and cornflour.
Add sugar, remaining white wine vinegar, and vegetables to the saucepan.
Return to a simmer and cook for 10 minutes while stirring.
Stir in the cornflour mixture and cook for 8-10 minutes until thickened.
Transfer the hot pickle into jars and seal after cooling.