Remove the casings from the fresh bratwurst sausage and discard casing.
Sauté the bratwurst sausage in a bit of vegetable oil over medium-high heat.
Remove the sausage once its browned and reserve the oil in the pan.
Add in the diced apple, raisins and chopped walnuts into the same pan and sauté a couple of minutes. Add the butter and cook until apples are softened. Re-add the sausage and Panko crumbs. Stir for about 30 seconds. Add the apple juice. Adjust the juice amount, as needed, so the stuffing mixture is not too thick or not too runny. Add rub or salt & pepper to taste. I used 2 Tbsp of the "HEB house" seasoning.
Refrigerate for an hour before proceeding to the next step - it needs to be cooled for food safety reasons if you don't want to cook the spiral loin immediately.
Fillet/butterfly your pork loin so you end up with a flat piece. Trim off excess ridges and thicknesses. Cover with plastic wrap and pound flat a bit with the smooth side of a mallet. Trim the sides squaring them up.
Lay the refrigerated bratwurst stuffing down leaving 1 inch borders. Roll into a spiral log - making sure to roll up the non-fat cap end first, so that the fat cap is on the outside of the roll. Wrap slices of bacon around pork tucking ends under next wrap as you go. Apply some rub or salt & pepper on the outside and wrap in Saran wrap. Store in refrigerator until ready to cook. I refrigerated overnight.
Heat pit to 250F, transfer cold loin from the fridge into your hot pit. Cook until the pork internal temperature is 140°F. (Note: add 1 tennis sized chunk of apple if using Kingsford briquettes). I smoked in the smoker for 1 hour using pecan chips and temps the same as above.
Remove from pit and loosely tent with foil for 15 minutes to allow it to cool and for juices to re-distribute.
While cooling, prepare glaze. Saute the butter & brown sugar in a pan. Add Karo syrup, apple juice and simmer to reduce to consistency of thin gravy. Pour over loin. If you like, you can set the glaze by returning the loin to the pit for 5 minutes. Slice into rings and serve.
