Pickled Swiss Chard Stems

["Toss chard stems, shallot, and salt in a colander set in the sink. Let stand 1 hour. Rinse and drain well.", "Meanwhile, toast mustard and caraway seeds in a small skillet over medium heat, stirring often, until mustard seeds begin to pop, about 2 minutes. Let seeds cool.", "Bring vinegar, sugar, and 1 cup water to a boil in a small saucepan; let cool slightly. Pour brine into jars. Let cool slightly, then cover and chill.", "DO AHEAD:", "Use the same salting method and brine, but instead of chard stems and shallot, use 1 sliced seeded peeled green papaya (about 1 lb.). Omit mustard and caraway seeds, and use 2 red or green Thai chiles and one 1""-piece peeled turmeric or ginger, thinly sliced.", "Use the same salting method and brine, but instead of chard stems and shallot, use 1 lb. fresh banana chiles (cut a long slit in each pepper to allow brine to penetrate) and 1 sliced peeled carrot. Omit mustard and caraway seeds, and use 1 garlic clove."]