Chop the pork into bite size chunks trimming the fat and reserving the bone for cooking.
Over high heat in a large stock pot preheat the oil. brown the pork making sure not to overcrowd the pot. Remove the pork and set aside.
Preheat the broiler on high and move the rack to the highest height setting. Using a half sheet pan, toss the tomatillos and jalapenos with 1 teaspoon oil. Broil the vegetables for 5 to 10 minutes or until blackened and blistered. Remove from the oven, flip, and repeat until the reverse side of the vegetables has been blackened (see notes).
To the stock pot used for the pork over medium heat, add the onions and cook until translucent. Add the garlic and continue to cook for another minute until you can smell the garlic bloom.
In a blender, add the tomatillos, jalapenos, green chilies, onion mixture, cilantro, oregano, cumin, chicken stock and pulse until desired consistency.
Pour the mixture into the stock pot and tomatoes.
Over medium high heat, add the pork bone and bring the mixture to a boil. put heat on low and simmer for 3/12 hours until the pork is tender and falling apart.
Lower temperature using an ice bath (see notes) or serve hot.