Season your pork chops on both sides with salt and pepper. This step is best done at least an hour before you begin cooking.
Heat 2 tablespoons of oil in a small saucepan over medium heat until hot.
Whisk flour into hot oil until smooth. Cook, whisking constantly until light brown. About 5 minutes.
Increase heat to medium-high and add the chicken stock in a thin stream, whisking constantly. Add the buttermilk and a small pinch of salt, whisking constantly. Bring to a boil then remove from heat.
Heat the remaining 2 tablespoons of oil in a 12-inch skillet over medium-high heat until smoking. Add the seasoned pork chops and brown for 3 minutes on each side. Remove to a plate.
Add sliced onions and a pinch of salt to your cast iron skillet and cook for about 10 minutes, until soft with brown edges. Halfway through cooking your onions stir in 1/4 cup of water while scraping all of the browned bits off the bottom of a pan with a wooden spatula.
After your onions are browned, stir in garlic, thyme, and another 1/4 cup of water. Cook about 30 seconds, scraping up any cooked on bits with a wooden spatula.
Return the pork chops to the skillet. Cover with onions then pour in the warm sauce. Put the heat diffuser under the pan and turn heat to low. Simmer covered for 10 minutes, or until an instant read thermometer shows the internal temperature of your pork chops to be more than 145 degrees, but less than 165 degrees.
Remove the pork chops to serving plates. Turn heat to high and cook sauce until it is reduced to a gravy consistency. Pour sauce and onions over pork chops.