Season the pork fillet all over with salt and freshly ground black pepper and place it in a large Ziploc bag or baking dish.
Make the marinade - whisk the marinade ingredients in a bowl until the brown sugar dissolves. Pour most of the marinade over the pork and squeeze the air out of the bag and zip closed if using or cover the baking dish with cling film. Marinate in the fridge for at least 1 hour or overnight.
When you're ready to cook, simply put the pork on to a hot barbecue or under a hot grill for 15 to 20 minutes, turning every 5 minutes, or until nicely charred. Every time you turn the meat, brush it generously with the leftover marinade so you build up a sticky glaze. Use a meat thermometer to check the internal temperature of the thickest part of the pork is 63C.
Transfer the pork to a platter and let it rest for 5 minutes, then serve garnished with sesame seeds and finely sliced spring onion.
Notes
Optional variations:
Spicier version – add more gochujang or Korean chilli flakes (gochugaru).
Honey garlic pork – add extra honey for a sweeter glaze.
Chicken version – the marinade works well with chicken thighs.
Beef version – use sirloin or bavette steak.
Korean pork skewers – cube or slice the pork before marinating. Skewers will only need 4 to 5 minutes on a hot barbecue.
Rice bowl – serve the cooked pork sliced over rice with vegetables and a fried egg.
This Korean barbecued pork fillet recipe is easily adapted if you’re cooking for less or more people.