Heat 1 teaspoon oil in a skillet. Add beans, onion, and chiles; heat through. Cool in a large bowl. Add tomatoes, cilantro, lime juice, and salt to taste; toss gently to combine.

Preheat grill. Place chicken in a plastic bag or between waxed paper sheets and pound with a heavy jar to flatten to an even thickness. Transfer to a large plate, brush both sides with 2 tablespoons oil, and season with salt and pepper. Grill, smooth side down, for about 2 minutes, or until edges turn opaque. Turn over and cook for 1½–2 minutes or until a meat thermometer registers 155–160°.

Remove chicken from grill, set on a plate, and cover. After 2 minutes, slice chicken thinly crosswise and add to tomato mixture, tossing gently to combine all ingredients.

Heat tortillas over an open flame or in a skillet. Keep warm in a folded napkin.

Set chicken-tomato mixture and tortillas on the table. To eat, hold a tortilla in one hand, scoop chicken mixture onto it, roll up, and enjoy.