1. In a large frying pan, heat oil over medium-high heat. Add chicken chunks and cook, stirring, until golden, about 4 minutes. Sprinkle corn-meal, chili powder, and cumin over chicken and cook, stirring, 1 minute. Stir in broth, tomatillos and chiles. Simmer, stirring often and mashing tomatillos, until sauce is slightly thickened, about 5 minutes. Stir in cilantro and simmer 30 seconds.
2. Warm tortillas in microwave-safe plastic wrap in a microwave oven for about 30 seconds on high. Spoon chicken with sauce into warm tortillas. Add lettuce. Roll up and eat by hand or with knife and fork