Toss the okra with 3 tablespoons kosher salt and let it sit in a colander for 1 hour over the sink to drain. Combine the vinegar, water, remaining salt, sugar, peppercorns, and mustard seeds in a nonreactive pot. When the okra has drained for 1 hour, rinse it thoroughly and let it drain. Bring the liquid mixture (brine) to a boil, and boil for 2 minutes. Place the okra and the onions in a nonreactive storage container, and pour the hot liquid over it. Stir occasionally until it cools, and refrigerate overnight. Will keep for 1 month in an airtight container in the refrigerator.
Yield: 1 pound. pickled okra