In a medium-sized mixing bowl, whisk together the spicy brown mustard, yellow mustard, maple syrup, brown sugar, apple cider vinegar, minced onion, soy sauce, black pepper, and garlic until well blended. The mixture should be smooth and aromatic.

Pour half of this vibrant mustard marinade into a gallon-sized resealable plastic bag. Set the remaining half aside for later use. Place the pork chops into the bag, ensuring each piece is fully coated in the marinade. Gently massage the chops to distribute the flavor evenly. Seal the bag securely, then place it in the refrigerator to marinate for a minimum of 2 hours. For deeper flavor, marinate overnight.

When ready to cook, preheat your grill or grill pan to medium-high heat. Lightly coat the grill grates or pan surface with non-stick cooking spray to prevent sticking.

Remove the pork chops from the marinade, letting any excess drip off. Discard the marinade in the bag. Season the chops lightly with kosher salt.

Place the pork chops on the hot grill, closing the lid. Sear each side for about 1 minute to develop a golden-brown crust. Lower the heat to medium and continue cooking for an additional 3 minutes per side. For a grill pan, skip the initial sear and cook each chop for about 3–4 minutes per side over medium heat, flipping carefully to avoid tearing the surface.

Transfer the cooked pork chops to a clean plate, tenting them loosely with aluminum foil. Allow the meat to rest for 5–10 minutes to lock in the juices before serving.

Serve the grilled pork chops with the reserved mustard marinade drizzled over the top or as a dipping sauce on the side for an extra burst of flavor.