Preheat oven to 350 degrees F. In a blender puree prunes with enough apple juice to make a smooth paste. Heat a skillet over high heat, season tenderloin and sear in oil until well-browned on all sides. Transfer to a baking dish and roast 8 minutes for medium-rare. In skillet sweat shallots in pan drippings until tender. Carefully add Armagnac, WATCH OUT it will flame; if not, ignite with a match. Shake pan until flames die out. Continue cooking, scraping bottom of pan too incorporate any browned bits. Add stock, onions, and prune puree and boil until reduced by half. Stir in 2 tablespoons of butter, just until melted. Set aside, keeping sauce warm.

To serve, melt remaining butter, add cooked noodles and toss to reheat and coat; season to taste with salt and pepper and mound on 2 dinner plates. Slice pork on bias, place atop noodles and spoon sauce over. Sprinkle with parsley.