Cut tomatillos in half and place on a baking sheet cut side down with unpeeled garlic. Broil on high about 5 minutes or until charred.
Remove everything from pan and place in bowl to cool.
Meanwhile, heat a large cast iron pan or stockpot over medium high heat.
Season pork chunks with salt and pepper. Add 1 tablespoon oil and half the pork in a single layer. Cook until seared on all sides. Remove and repeat until all the pork is browned.
Reduce heat to medium. Add chopped onion, bell pepper and 1/4 teaspoon salt to pan. Saute until softened.
Peel garlic and place in a food processor with the cooled tomatillos, jalapeno, cilantro and oregano. Pulse until smooth. Makes about 3 cups of green salsa. Keep 1 cup for to serve with your meal and reserve the rest.
Add pork back to skillet with the softened green bell peppers and onions. Pour 2 cups of green salsa over pork mixture and add chicken stock to cover.
Bring to a boil then reduce heat and simmer uncovered 2-3 hours or until tender.