Preheat oven to 350F. Place rack in middle position. Spray 13x9 pan with nonstick spray.
In prepared pan, place uncooked rice, cayenne pepper, soup, sour cream, and 1 cup of stock, 1 tablespoon of parsley, and ½ teaspoon salt. Stir together in pan.
Combine 2 ½ teaspoons salt, pepper, onion powder, garlic powder, smoked paprika, and ½ teaspoon dried thyme in a small bowl. Stir together. Season both sides of the pork chops
In a 12-inch skillet, heat 2 tablespoons oil over medium-high heat. Once hot, add pork chops and cook for about 3 minutes on the first side until golden brown. Flip and continue cooking for 2 minutes. Remove from pan and set aside on a plate.
Quickly add butter, mushrooms, onion, bell pepper, and celery to the pan. Cook until the onions become translucent, the celery softens, and the mushrooms have given up their liquid, about 5-6 minutes. Add in garlic, remaining ½ teaspoon thyme, and final ½ teaspoon of salt and continue cooking for about 1 minute. Pour in remaining ½ cup stock, vinegar, and mustard. Quickly bring to a boil, then remove from heat and stir into ingredients in 13x9 pan.
Nestle pork chops partway into creamy mixture. Cover with foil. Bake for about 45-50 minutes, until rice is cooked and pork chops reach 145F on a digital thermometer. (Depending on thickness of pork chops, they may be finished cooking before the rice is ready. Check them at 30 minutes, and remove them from the pan, if necessary. Recover the rice and continue cooking.)
Remove from the oven, let sit for 10 minutes before serving. Uncover, garnish with final 1 tablespoon of parsley and serve.