Preheat the oven 325°F. Season the pork with salt and pepper. Heat the oil in a large, heavy-bottomed skillet set over medium-high. When hot, brown the pork in batches, and then transfer to a large casserole. (The casserole used in this recipe was 10¡± x 14¡±.)
When the pork is browned, add the onion, bell pepper, poblano pepper and garlic to the skillet and cook 2 minutes. Mix in the salsa verde, stock, oregano, chili powder and brown sugar.
Bring to a simmer, and then pour mixture over the pork. Cover and cook pork in the oven 90 minutes, or until very tender. Stir in the cilantro, taste and adjust seasoning, if needed, and serve.
Note: Poblano peppers are a rich green, mildly spicy pepper available in the produce department. If unavailable, replace with another green bell pepper. Jars of salsa verde are available in the Mexican foods aisle.