Heat the vegetable oil in a large dutch oven over medium low heat. Add the onions and cook, stirring occasionally, until translucent. This takes about 5 minutes. Stir in the garlic and cook another 30 seconds. Reduce heat to low.
Mix in the gochugaru, gochujang, shiro miso, mirin, soy, apricot jam and sesame oil. Stir to combine.
Add the chicken stock and bring to a simmer.
Add the ribs to the dutch oven. Stir. The liquid won't cover the ribs. That's OK. Resist the urge to add more stock. Put a sheet of aluminium foil over the dutch oven and cover tightly. Place the pot in the pre-heated oven.
After 30 minutes, remove the pot. Using tongs, move some of the submerged ribs up. Move the ones that were on the top down. Basically mix them up. Replace the foil and lid and return to oven.
Continue to cook for another 30-40 minutes. Check at 30 minutes. They should be fork tender but if they aren't cook them another 10 minutes. Cook them until they are tender. Tender doesn't mean mush. Mush is bad. Tender means they pull away cleanly from the bone. Maybe a little tug to get them off but the bone winds up clean.
Remove the pot from the oven. Remove the ribs to a bowl and tent with foil.
Put the sauce in a large cup or fat separator and spoon off the fat. Return the sauce to the pot. Over medium heat, reduce the sauce until it's fairly thick - like a thin BBQ sauce. This should only take around 5-8 minutes if you resisted the urge to add more liquid while cooking.
Return the ribs to pot and toss in the sauce. Garnish with sesame seeds. Serve with rice and a nice green salad. Or forget the sides and just mow down on ribs.