For the celery: Butter a shallow ovenproof pan with 1 tablespoon of the butter, place the celery in the pan, and season it with salt and pepper. Add the chicken stock to the pan to cover the celery by 3/4. Bring the liquid to a boil over high heat, cover the pan, and transfer it to a preheated 400 degree oven. Bake the celery for 35 to 40 minutes, or until it is tender. Drain the cooking liquid, reserving the celery, into a large casserole and reduce it over high heat to about 2 tablespoons. Add the remaining butter, a little bit at a time, until it is emulsified and keep the celery sauce warm. Keep the reserved celery hot.
For the mustard sauce: In a medium skillet melt the butter, add the shallot and the thyme, and cook the shallot over moderately high heat until it is just caramelized (a light blond). Deglaze the pan with the wine and reduce the liquid over high heat until it is almost evaporated. Add the veal stock and reduce it for 2 to 3 minutes. Add the cream and reduce the liquid for 2 to 3 minutes, or until it starts to thicken. Add the mustard to taste, season the sauce with salt and pepper, and strain it through a fine sieve. Reserve the sauce.
For the pork: Cut the pork into 4 pieces and season each piece on both sides with salt and pepper. Using a small spatula spread the Dijon mustard over each piece of pork. In a bowl combine the mustard seed and the bread crumbs, roll each piece of pork in the crumbs, and reserve the pork. To a preheated skillet melt enough peanut oil and butter to just cover the pan, heat the oil and butter over moderately high heat until it is hot, and add the pork. Cook the pork on 1 side until it is colored. Transfer the skillet to a preheated 400 degree oven and bake the pork, turning it to the uncooked side, for about 4 to 5 minutes, until the inside is just pink. Arrange the Spring Potato Puree on a platter, put the celery beside it, and glaze it with the warm celery sauce. Put a small ladle of the mustard sauce on the platter and arrange the pork, each piece cut into 3 slices, over the sauce. Garnish the dish with the herbs and serve the remaining sauce in a sauceboat.