Whisk together the oyster sauce, Dijon mustard, hoisin sauce, ginger, honey and soy sauce in a bowl until combined; stir in the spring onions. Spread about 1/4 of the mixture into the bottom of a rectangle baking dish. Arrange the pork chops over the sauce in a single layer then pour the remaining sauce over the chops, covering them completely.
Bake in the preheated oven until the chops are no longer pink at the centre and the juices run clear, 30 to 40 minutes. Baste once or twice while baking.
Drain the liquid in the baking dish into a saucepan. Turn on the oven's griller then place the chops underneath the griller until caramelized and brown, 1 to 2 minutes.
Whisk the cornflour with water in a small bowl then whisk the mixture into the pan juices. Set the saucepan over medium heat then bring the sauce to a simmer, whisking constantly until thickened, 1 to 2 minutes. Season to taste with salt and black pepper. Serve sauce with chops.
I keep peeled ginger in the freezer, cut into chunks, so when needed I just take a chunk out and grate it, so I always have fresh ginger at hand.