Preheat the oven to 150C/300F. Place a large casserole pan on the hob, add 1 tbsp of the oil and heat until very hot.
Season the pork with the salt and pepper and place in the pan with the hot oil. Seal on all sides.
Pour the stock over the pork.
Add in the onion, the whole carrot, celery, garlic and ginger.
Now add the mirin, soy sauce, gochujang and the red chilli. Bring to the boil, then place a lid on the pan and place in the oven for 4 hours. NOTE: Check two or three times during cooking, and top up with a little boiling water if needed. You’ll need at least 1 litre of liquid left by the time the pork finishes cooking.
Take the pan out of the oven and place the pork on a chopping board. Remove and discard the layer of fat. Shred the pork using two forks.
Place a sieve over a large bowl and strain the cooking liquid. Throw the strained vegetables away and place the liquid back in the pan with the shredded pork. Leave on a low heat to keep warm.
Place the eggs in a small pan. Just cover with cold water. Bring to the boil, then simmer for 6 minutes.
Remove the eggs from the heat and place in a bowl of cold water to stop the cooking process.
If you're using dried noodles, place the noodles in a pan of boiling water and boil for 5 minutes. Then drain, run under cold water (to stop them sticking) and put to one side.
Heat the remaining oil in a frying pan.
Add the leek, season with a pinch of salt and pepper then fry for 5 minutes, stirring a couple of times.
Push the leeks to one side of the pan and add the spinach to the pan. Allow to wilt for 1 minute.
Divide the noodles between four bowls. Top with the hot broth, shredded pork, leek, spinach and carrot matchsticks.
Carefully peel the two eggs and slice in half. Place 2 halves in each bowl.
Garnish the soup with spring onions, then sprinkle with the white and black sesame seeds and the chilli flakes before serving.
Notes
Can I make it ahead?
You can make the pork and liquid ahead, but I would recommend making the toppings right before serving.
Cook the pork, then shred it and strain the stock. The pork and strained liquid can be placed in a container together with a lid on and refrigerated for 2-3 days.
Reheat over a medium heat in a pan.
Make all of the toppings as per the recipe as the pork is reheating.
Can I freeze it?
Yes. You can make the pork and liquid ahead, but not the other toppings/additions.
Cook the pork, then shred it and strain the stock. The pork and strained liquid can be placed in a container together with a lid on and frozen.
Defrost in the refrigerator overnight.
Reheat the pork and liquid over a medium heat in a pan.
Make all of the toppings as per the recipe as the pork is reheating.
Make it in the slow cooker:
You can cook the pork in the slow cooker. Cook as per the recipe up to the point you add the sliced red chillies in step 5. Then transfer to a slow cooker and cook for 7-8 hours on low or 6-7 hours on high. Once the pork is cooked, continue on with the recipe as per the instructions.
Ingredient substitutions/swaps:
You can replace the mirin with Chinese rice vinegar or rice wine vinegarSwap out the baby spinach for pak choi or sliced spring greensAdd extras such as fried mushrooms, fresh radish slices or crispy seaweedNutritional information is per serving.