Preheat oven to 400℉. In a cast iron or other oven-safe pan, melt butter and oil. Add onions and saute for 5-6 minutes, or until soft.
Add 3-4 tbsp beef stock to onions and let cook for 10-15 more minutes, until tender.
Add minced garlic and saute for 2 more minutes, or until fragrant.
Season pork chops with salt and pepper.
Remove onions from pan, but do not wipe out your skillet. Place pork chops in pan and cook for 4-5 minutes on each side, or until golden. Remove pork chops from pan.
Add onions back to pan. Sprinkle flour on top and mix to combine. Cook for 1-2 more minutes.
Add remaining beef stock to pan. Let simmer for 4-5 minutes, or until sauce has thickened slightly.
Place pork chops back into pan. Spoon broth mixture on top of pork chops. Top with provolone and gruyere cheese.
Transfer pork chops to oven and cook for 7-9 minutes or until cheese is melted and bubbly. Garnish with fresh parsley and serve!