Arrange pork chops in a shallow baking dish and pour Bulgogi marinade over top, turning chops to coat. Cover and marinate for 30 minutes at room temperature, or up to 24 hours in the fridge (in which case, bring to room temperature prior to grilling).
Bring a large pot of well-salted water to a boil. Prepare an ice bath by filling a large bowl with ice and cold water.
Prepare a gas grill for indirect grilling (by lighting only half of the burners) and preheating for 10 minutes, or preheat a grill pan for 5 minutes over medium-high heat.
Arrange chops on unlit side of the grill, letting excess marinade drip back into the baking dish, and immediately close the lid. Transfer marinade to a medium saucepan.
Cook chops for about 8 minutes, then flip, close the lid again, and cook a few minutes more. Transfer chops to the direct heat side of the grill until lightly charred and cooked to 160ºF. Move to a plate and tent with foil to rest for 5 minutes.
While chops are cooking, whisk corn starch into water until no lumps remain, then whisk into the reserved marinade. Bring to a boil over medium-high heat, then reduce to a simmer and cook until thick and glossy, about 10 minutes.