Start by preparing the stuffing. Heat the oil in a large frying pan over medium heat, add the chopped onion, cover with a lid, and cook gently for about 15 minutes, stirring occasionally, until the onion becomes soft and translucent.
Remove the lid and increase the heat to high. Add the mushrooms to the pan and stir-fry for 2–3 minutes until they release their moisture and start to brown. Toss in the spinach and continue stir-frying just until it wilts down completely. Stir in the bread crumbs, season generously with salt and pepper, and mix everything together well. Remove from the heat and let the stuffing mixture cool.
Brush both sides of each pork chop with oil and season well with salt and pepper. Position them under a preheated hot broiler, about 4 inches (10cm) from the heat source, and broil for 7–8 minutes on each side until the chops are cooked through and develop a golden brown color.
Remove the chops from the broiler briefly and spoon 1 tablespoon of the cooled stuffing mixture on top of each one. Place a slice of cheese over the stuffing on each chop, then return them to the broiler for 3–4 minutes until the cheese melts and becomes bubbly and lightly golden.
While the cheese is melting, heat a small amount of oil in a small nonstick frying pan over medium heat. Add the remaining stuffing to the pan, then press it down firmly with a wooden spoon to form a thick, even pancake shape that covers the base of the pan.
Cook the stuffing pancake for about 5 minutes without disturbing it, allowing the underside to turn brown and crispy. Transfer the frying pan under the broiler for 2–3 minutes to brown and crisp the top surface. Carefully flip the stuffing pancake upside down onto a cutting board or plate and slice it into 6 equal wedges.
Serve each broiled pork chop hot with a crispy stuffing wedge on the side for a delicious combination of textures and flavors.