Trim off any excess fat from the pork and cut into 2 inch squares. In a large (6 to 8 quart) stock pot, over a high heat, sear the pork in the vegetable oil until golden brown. Remove the pork from the pot and pour off any oil or fat drippings, but leave 2 tablespoons of oil. In the same pot, over a medium heat, add the chopped onion, garlic, salt, and pepper and saute until transparent. Add the cumin, pork, and chicken stock, and cook for 1/2 hour.
Add the poblanos, jalapenos, and bell peppers. Puree the tomatillos and cilantro in a blender. Add them to the pot and cook an additional 30 to 45 minutes. Serve with white beans and rice. Garnish with grated sharp white cheddar cheese.