Heat-up a Dutch oven over a medium flame. Add 1 Tbl of peanut oil and 1 Tbl of butter to sear the chops. Brown the chops on both sides, then remove. Degrease the pan. Melt 2 Tbl of butter in the pan and throw the onion rings in. Season the onions with salt and sweat them down - somewhat. Return the chops to the pan. Add tarragon, pepper and garlic. Reduce the flame to low and cover. Braise the chops for 1 - 1 1/2 hours, turning them periodically. Remove the chops from the pan and reduce the sauce over medium heat. When appropriately reduced, add the mustards. Simmer for a minute. Return chops to the pan and cut off heat. Allow the dish to rest for 5 minutes.