Preheat oven to 400 degrees F.
Heat the oil in a skillet over moderately low heat. Add the onion and garlic and cook until softened. Add the garlic, cumin, and chili and cook for 1 more minute. Add the beans and 1/2 cup water, and cilantro cube, cover and simmer for 5 minutes. Mash the beans with the back of a fork and season with salt and pepper, to taste. Combine the chicken, 1/2 cup cheddar, chiles, and salt and pepper, to taste and toss well.
Warm the tortillas wrapped in a towel in a microwave for 3 minutes.
Spread 1/8 of the bean mixture on top of each tortilla, top with 1/8 of the chicken mixture and roll the tortillas up. Arrange them seam side down in a baking pan, top with remaining cheddar, and cover with foil. Bake for 15 to 20 minutes or until warmed through. Serve topped with sour cream and lettuce.
Recipe courtesy of Sara Moulton