Preferably over a flame, char poblano peppers until skin is blackened and blistered. Place in a grocery bag or wrap in a kitchen towel and let steam and cool off enough to handle.
If you do not have a gas stove, set your oven to broil. Place peppers in a pre-heated oven as close to the heating element as possible. Using long tongs, turn peppers frequently until blistered and charred.
Using a paper towel, wipe the skin off the peppers. Cut a pocket in the pepper (lengthwise), remove and discard seeds and veins.
In a bowl, combine the softened cream cheese and Monterey Jack cheese. Separate mixture into four equal portions and shape into ovals. Stuff each pepper with a portion of the cheese mixture. Snuggling the pepper around the cheese.
In a medium skillet, add oil, diced onion and rice. Sauté over medium heat until the rice turns opaque and white in color. Add warmed broth to the pan. Bring to a boil, taste the liquid for seasoning and add salt and pepper as needed. If using corn, sprinkle the corn over the peppers and boiling broth. Cover, reduce heat to medium low and cook for 25 – 30 minutes or until the liquid is evaporated and rice is cooked through. Turn the heat off and let the rice rest covered and undisturbed for 10 – 15 minutes.