A vibrant golden Dutch condiment of crisp cauliflower florets, gherkins, and silver-skin onions pickled in a tangy cider vinegar sauce spiced with turmeric, mustard, and ginger.
In a large ceramic bowl, toss the cauliflower florets, diced gherkins, and silver-skin onions with the sea salt. Let stand for 20 minutes to draw out excess moisture and preserve their crunch, then rinse quickly in cold water and drain.
In a non-reactive saucepan, combine 200ml of the cider vinegar and the sugar, bringing to a simmer over medium heat until the sugar dissolves completely.
In a small jug, whisk the remaining 50ml vinegar with the mustard powder, ground turmeric, ground ginger, and flour into a smooth, bright yellow paste. Whisk this paste into the simmering vinegar and cook for 3 minutes until thick and glossy.
Tip the drained vegetables into the bubbling mustard sauce and simmer gently for just 4 minutes so the vegetables remain crisp. Spoon the hot piccalilli into sterilised jars, seal, and let mature before serving with cheese or cold meats.