Roast and peel poblanos. Cut pork into 2-inch chunks. Brown pork in olive oil; remove from pot. Dice onion and saute. Return pork to pot. Add cumin, salt and pepper. Add chicken broth and poblanos. Simmer until pork is tender. Remove pork. Let broth cool. Put unstrained broth into blender with jalapenos, tomatillos and cilantro. Blend thoroughly. Put liquefied broth and pork back into pot. Do not let it come to a boil. Just before serving add juice of one lime. Serve over rice and top with shredded Monterey Jack cheese, if desired.