This recipe is adapted from Judy Rodger's . I've always ended up with more than 2 pints when I made it, so I've adjusted the amounts to yield 3 pints and streamlined the method a bit (the book has you salt and drain the vegetables first, the difference in final texture is, to most people, negligible). You still end up with sweet and kicky zucchini slices that are crunchy, brightly flavored with mustard, and a brilliant chartreuse color from turmeric. Zuni Cafe in San Francisco serves them with their famously juicy hamburger. I do that too, but I also like to put them out when we have sausages or any grilled meat, or add them to a classic relish tray for a bit of extra color..
- First make the brine. Put the cider vinegar, sugar, and salt in a small saucepan. Put over medium-high heat and bring to a boil. While that's heating up, crush the mustard seeds—you can use a mortar and pestle if you have them, or put the seeds in a resealable plastic bag and pound them gently with a rolling pin, flat meat tenderizer, or a small frying pan. Add the crushed mustard seeds, dry mustard, and turmeric to the vinegar mixture.
- Once the mixture boils, reduce the heat to low so the mixture simmers gently. Let it simmer for 3 minutes. Remove the pan from the heat, pour the mixture into a large bowl, and let cool until just warm to the touch.
- Meanwhile, cut the zucchini into slices 1/8- to 1/16-inch thick. A mandoline, if you have one, is very handy for this, but a sharp knife and steady hand work just as well. You can cut the zucchini crosswise or lengthwise—the choice is yours!
- Trim the root end of the onion. Cut it in half lengthwise and remove the peel. Set the 2 halves on a cutting board, cut side-down, and thinly slice the onion.
- When the brine is cooled, add the zucchini and onion slices (you want the brine truly just barely warm, if that, because you want the vegetables to stay raw, getting a bit tender just from their time in the brine, not from being cooked by heat). Stir to coat the vegetables completely with the brine.
- Divide the zucchini and onion evenly between the 3 pint jars, leaving about 1 inch of space between the tops of the vegetables and the tops of the jars. Add enough brine in each jar to cover the vegetables, leaving at least 1/2 inch space between the top of the liquid and the tops of the jars. Use a paper towels to wipe the rims and edges of the jars clean. Screw on the lids. Put in the fridge and let chill for at least 1 week and up to 6 months (although when I lost track of a jar in the back of the fridge once, we still ate the pickles and they were just fine).