In a medium heatproof bowl, whisk together the boiling water, brown sugar and 2 tablespoons salt until sugar and salt are dissolved. Stir in the ice cubes to cool the brine. Add the pork chops, the cover bowl with plastic wrap, and refrigerate for 30 minutes. Remove the chops from the brine, rinse well, and dry thoroughly with paper towels. (If you’re really in a hurry you can skip the brining step, but I find it does make a difference for ultra moist and tender pork chops.)
Heat the oven to 350°F. In a 10-inch cast iron skillet, heat the oil over medium-high heat. When the oil is shimmering, add the pork chops and sear until well browned, about 2 minutes per side. Transfer to a plate and cover to keep warm.
To the same skillet, add the butter, followed by the onion, cabbage, sweet potato, thyme, and bay leaf. Season with salt and pepper. Cook, stirring often, until the cabbage and onions are wilted and caramelized, about 5 minutes.
Place the seared pork chops on top of the vegetables. Transfer to the oven and bake until the pork chops are cooked and the internal temperature registers 145°F when measured with an instant-read thermometer, 8 to 10 minutes.
Transfer the pork chops to serving plates. Taste the vegetables and adjust the seasoning as needed with salt and pepper. Stir to make sure all of the vegetables are coated with the buttery cooking liquid. Divide the vegetables between the plates and serve immediately with mustard, if desired.