In a large bowl, combine the vegetable oil, whole grain mustard, Dijon mustard, crushed juniper berries, minced garlic, paprika, caraway seeds, marjoram, thyme leaves, black pepper, and salt. Mix well to form a paste.

Score the pork chops lightly on both sides with a sharp knife, making shallow cuts about 1cm apart. This helps the marinade penetrate the meat.

Coat the pork chops thoroughly with the marinade, layering the onion rings between and on top of the chops. Cover and refrigerate for at least 2 hours, or ideally overnight for best flavour.

Remove the pork chops from the refrigerator 30 minutes before grilling to bring them to room temperature. Reserve the onion rings from the marinade.

Preheat your BBQ grill to medium-high heat, approximately 200-220°C. Clean and oil the grates well to prevent sticking.

Place the pork chops on the grill and cook for 5-6 minutes per side without moving them, to develop good char marks. Add the reserved onion rings to a cooler part of the grill.

Continue grilling, turning occasionally, until the pork chops reach an internal temperature of 63°C measured with a meat thermometer inserted into the thickest part away from the bone. Total cooking time is approximately 12-14 minutes.

Remove the pork chops from the grill and rest for 5 minutes under loose foil. During resting, the internal temperature will rise to a safe 65-70°C ensuring the pork is safely cooked while remaining juicy.

Serve the Schwenkbraten topped with the grilled onions, garnished with fresh parsley and accompanied by lemon wedges for squeezing.