Not only is this casserole a good source of niacin (mainly from the chicken), but one serving also supplies about 60 percent of your daily calcium needs. Fresh corn and corn tortillas offer an ample amount of folate, too.
Cut poblanos and bell pepper in half lengthwise; discard seeds and membranes. Place poblanos and bell pepper, skin sides up, on a foil-lined baking sheet; flatten with hand. Place corn on baking sheet. Broil 10 minutes or until poblanos and bell pepper are blackened and corn is lightly browned. Place poblanos and bell pepper in a zip-top plastic bag; seal. Let stand 10 minutes. Peel and coarsely chop; set poblanos and bell pepper aside separately. Remove corn kernels from cobs.
Lightly spoon flour into a dry measuring cup; level with a knife. Place flour, 1/2 teaspoon salt, and black pepper in a large saucepan. Gradually add milk, stirring with a whisk. Cook over medium heat until slightly thick (about 12 minutes), stirring constantly. Remove from heat. Combine 1 cup milk mixture and poblanos in a blender; process until smooth. Stir pureed poblano mixture into remaining milk mixture.
Preheat oven to 350°.
Combine bell pepper, corn, remaining 1/2 teaspoon salt, 1 cup Mexican cheese, red onion, cilantro, eggs, and ricotta.
Coat bottom of a 13 x 9-inch baking dish with cooking spray. Spread 1/2 cup sauce in bottom of dish. Arrange 6 tortillas over sauce, overlapping slightly. Spread half of ricotta mixture over tortillas; top with half of chicken. Sprinkle with 1/3 cup green onions and 2/3 cup Mexican cheese. Pour about 1 cup sauce over cheese. Repeat layers with 6 tortillas, remaining ricotta mixture, remaining chicken, 1/3 cup green onions, 2/3 cup Mexican cheese, 1 cup sauce, and 6 tortillas. Pour remaining sauce over tortillas. Coat 1 side of foil with cooking spray. Place foil, coated side down, over casserole. Bake at 350° for 30 minutes or until bubbly.
Uncover; sprinkle with remaining 2/3 cup Mexican cheese and 1/3 cup green onions. Bake, uncovered, 15 minutes or until cheese melts. Let stand 15 minutes.
MyRecipes is working with Let's Move!, the Partnership for a Healthier America, and USDA's MyPlate to give anyone looking for healthier options access to a trove of recipes that will help them create healthy, tasty plates. For more information about creating a healthy plate, visit www.choosemyplate.gov.