Brine: in a nonreactive container or resealable plastic bag combine the spring water, Gewurztraminer, sugar, citrus zest and juice, grapeseed oil, salt, peppercorns, and bay leaves. Set aside.
Remove the pork loin from the package and pat dry to remove all the liquid, wash the pork loin under room temperature water and repeat the pat dry method. Next, trim some fat from the top of the pork loin and place the loin in the brine. Refrigerate for 24 hours below 41 degrees F or lower.
Remove the pork and discard the brine. Lightly pat it dry and place it on a flat 1/2 sheet pan, lightly wrap in plastic, and put into the freezer. When the pork is slightly frozen, using a machine slicer (deli slicer) slice the frozen pork paper thin. Portion the pork loin into 6 servings of 5.6 ounces each if just a little heavy that is fine you have room for error with the extra ounces. Put each portion on small deli sheets or parchment paper and place them in the refrigerator until ready for use. Be sure to properly sanitize the deli slicer and wash it in hot soapy water.
Finishing the sandwich: Preheat a large flat top "Philly Style" gas griddle about 26 by 18-inches to 350 degrees F for 5 minutes. Pour 4 tablespoons grapeseed oil in the center of the griddle, spread evenly and let the oil get hot. Place the julienne onions on 1 side of the griddle and let them caramelize about 4 minutes. On the other side of the griddle, place the ground bratwurst and let cook through to an internal temperature of 155 degrees F. Chop the brats into smaller crumbles. When the brats and the onions are fully cooked, about 5 minutes more, toss them together and to one side of the griddle on low-heat (160 degrees F for hot holding). On the side that you just removed the brat and onion mixture, place the kraut and the julienned apples and cook until tender, another 4 minutes. When the kraut and the apples are fully cooked toss them together with the onions and brat's. Deglaze with the beer and reduce until it has evaporated. Hold the apple mixture with the onion and brats on the cooler part of the griddle.
Remove the shaved pork loin from the refrigerator. Drizzle the last 4 tablespoons grapeseed oil on the part of the griddle that is at 350 degrees F and cook the shaved pork loin about 5 minutes. Lightly rough chop the shaved pork loin "Philly style"- place 1 spatula on a section of the pork loin and hold firmly and with a second spatula pull gently apart (pull away from each other and away from your body). When the shaved chopped pork loin is fully cooked and no visible blood, be sure it is fully chopped "Philly style" toss with the warm kraut, onion, apple, and brats, and section into 6 (6-ounce) portions on the griddle. Top each portion with 2 ounces Limburger cheese. Place 1 sliced pumpernickel hoagie roll on top of the melted cheese/pork portion and place a spatula under it. Place one hand on top of the roll and flip sunny side up while catching the pork-melted cheese stuffed roll in the same hand that you use to place on the roll.
Serve with mustard, German pickles and German beer.
The proper way to eat this sandwich is called the "South Philly Slump" place the sandwich in your hands lengthways, starting at one end only of the sandwich, duck your buttocks out away from you (in a duck position) and lean slightly towards the front, so that you do not drip all over yourself. The proper way to order this sandwich is: . 1."Pork wit" which means " everything and with cheese" . 2. "Pork wit-outenzi" which means "no cheese only" .