Preheat oven to 350 degrees.
To make the enchiladas: In a large skillet, heat the oil over medium-high heat. Add the onion and cook for 5 to 7 minutes, until softened. Stir in the diced green chilis, cumin, garlic powder, and red pepper flakes. Season with salt. Stir in the shredded chicken and 1/2 cup of the enchilada sauce. Remove from the heat.
To assemble the enchiladas, set up an assembly line including tortillas, enchilada sauce, beans, chicken mixture, both of the cheeses mixed together, and scallions. Lay out a tortilla on a flat surface and spoon 1 tablespoon of the refried or black beans in a line down the center of the tortilla. Add equal amounts of the shredded chicken mixture, 2 tablespoons of the cheese, and 1 tablespoon of the scallions, and roll them up. Repeat with the remaining tortillas and fillings.
Pour another 1/2 cup of the enchilada sauce in the bottom of a 9 by 13-inch baking dish and place the rolled-up tortillas in the dish. Spread the remaining enchilada sauce on the top of the tortillas and sprinkle on the remaining shredded cheese. Bake uncovered for 20 to 25 minutes until the cheese is melted and bubbly.
To make the cumin crema: Stir together the sour cream and cumin in a bowl. Remove the enchiladas from the oven and serve immediately, garnished with the remaining scallions, some cilantro, and a drizzle of cumin crema.