Cut the bacon slices crosswise into 1/2” wide pieces.
In a large Dutch oven set over medium heat, cook the bacon until nice and crispy. Remove to a plate with a slotted spoon and set aside.
Add the onions and salt to the Dutch oven and cook, stirring often, until caramelized - about 15-20 minutes. Add paprika and black pepper and stir until well combined.
Add shredded cabbage and cook, stirring, for a few minutes until all the ingredients are evenly distributed, then throw in apple dice and cooked bacon.
In a large measuring cup, mix the chicken stock, apple cider vinegar, Dijon mustard, spices and chopped rosemary together with a whisk. Pour that over the cabbage and stir to combine, then cook over medium heat for about 15 minutes, until the cabbage is softened and the liquid is almost completely evaporated.
Add the toasted hazelnuts and fresh parsley, mix them in let this rest for 10 to 15 minutes, then give one final toss and serve.
This will keep for up to 5 days in the refrigerator and actually tastes better after it's had a chance to sit for a day or two.