Cut off the top of the head of red cabbage and set the lid aside for later. Hollow out the head of red cabbage, cut the removed cabbage into smaller pieces, and add it to a bowl with the cubed pork loin and diced onions.
Using a mortar and pestle, grind the roasted garlic, salt, paprika, nutmeg, allspice, cloves, and cinnamon stick into a uniform paste.
Add the paste to the bowl with the cabbage, pork, and onions, mix to combine, and spoon the mixture into the hollowed-out head of cabbage.
Grate the boiled potatoes into a bowl, add the bacon, shallots, salt, and pepper, and mix to combine. Line a round baking pan with parchment paper, press the mashed potatoes into the pan, and make an indentation in the middle.
Place the stuffed head of cabbage on top of the indentation in the middle of the mashed potatoes and pour the vegetable broth over the seasoned pork mixture. Place the cabbage lid back on top of the stuffed red cabbage and pour the melted butter over the entire thing. Transfer the baking pan to a preheated oven and cook at 325°F for 2 hours and 30 minutes. If the red cabbage starts to get too dark, slightly reduce the oven temperature.
Garnish the stuffed red cabbage with sour cream and parsley before serving.