To make sauce: In a small bowl, combine flour, chili powder, cocoa powder, sugar and salt; set aside. In a medium saucepan, add tomato sauce, water and tomato paste. Heat and stir in flour mixture using a whisk. Continue stirring over medium heat while sauce thickens. Simmer slowly for 30–60 minutes, stirring occasionally.
To make filling: Cook chicken breasts in a pot of boiling water until done, approximately 20 minutes. Cool and cut into 1/2-inch (2cm) pieces. Drain and rinse canned black beans. In a medium bowl, combine chicken, beans, 1 cup (130g) cheese, green chilis, cumin and garlic powder.
Preheat oven to 400°F (205°C).
Spray a 9x12-inch (22x30cm) shallow baking pan with vegetable oil spray. Pour one cup enchilada sauce into the baking dish and spread evenly. One at a time, moisten each tortilla by dipping it briefly in the enchilada sauce. Place approximately 1 cup (150g) of filling on each tortilla and roll it up. Put in baking dish seam side down. Continue this process until all enchiladas have been assembled. Pour remaining sauce over enchiladas.
Bake in the oven uncovered for 20–25 minutes. Remove and sprinkle over remaining cheese. Return to oven for 5 more minutes.
Serve with salsa and light sour cream.