Preheat oven to 350 degrees. Line a large rimmed baking sheet with foil and spray with non-stick cooking spray.
Cut the 3-4 bell peppers in half from top to bottom and remove the ribs and seeds. Place on the prepared baking sheet.
In a large bowl, combine the 3 cups chicken, 8 oz. cream cheese and 1 cup of the shredded Colby Jack cheese. Stir in 1 jalapeno, 1 10 oz. can green enchilada sauce, 1 15 oz. can black beans, 1 cup frozen corn, 1 4 oz. can chopped green chilies and stir to mix well.
Stir in the 1 teaspoon chili powder, 1/2 teaspoon cumin, 2 cloves garlic and salt and pepper, to taste. Stir in the 1/4 cup cilantro if using.
Divide the chicken mixture evenly among the peppers. Sprinkle with the remaining cheese.
Bake for about 25 minutes, or until the peppers are just tender and the filling is hot. Turn on the broiler and bake an additional 2-3 minutes until the cheese is bubbly and golden.
Let stand 5-10 minutes before serving. Serve with sour cream and salsa if desired.