½ cup apple cider vinegar
2 tablespoons yellow mustard seeds
4–5 pounds mixed root vegetables (such as parsnips, kohlrabi, celery root, turnips, and rutabagas), peeled, cut into 1” cubes
½ pound thick-cut applewood-smoked bacon, diced
1 large white onion, diced
1 tablespoon (packed) dark brown sugar
Kosher salt and freshly ground black pepper
2 tablespoons chopped flat-leaf parsley