My butcher always has nice boned pork loin joints in the shop, generally for cutting off individual pork steaks, which are great for tonkatsu or similar breaded cutlet and escalope-type dishes, but they are also good for roasting.
I made a marinade from dark and light soy sauces, Chinkiang black rice vinegar, sesame oil and honey. I stabbed the pork all over with a thin knife and marinated the pork for 24 hours, turning it frequently. I find that zip-top freezer bags are good for marinating meat, because they have a tight seal and it makes turning the meat a simple and clean business. They also take up less room in the fridge than a bowl and you need less marinade to cover the meat properly.
I cooked the meat in a foil-lined roasting tray with its marinade(these marinades can stick really hard to your oven ware), with the foil wrapped loosely over the top and sealed to create a kind of tent for the first 45 minutes. Then I opened the foil up and gave it a further 45 minutes, basting frequently.
When the pork was done it looked quite blackened on top, but it wasn’t at all burnt. It was just the colour that the honey and soy had turned in the oven.
I made a chilli sauce to accompany this. I could have used a bottled sriracha sauce but I had some red chillies in the fridge to use up. I seeded the chillies and put them in a processor with a thumb of fresh ginger, two cloves of garlic, some fish sauce, a splash of sunflower oil, white rice vinegar, a knob of palm sugar and a squeeze of tomato purée and blended this until smooth.
I carved the pork and served it with steamed jasmine rice and steamed pak choi, with the roasting juices and marinade spooned over the top, and the chilli sauce on the side.