2 teaspoons vegetable oil 4 boneless, skinless chicken breast halves (about 1 pound total), cut into 1/2-inch cubes 1/2 cup water 1 (1-1/4-ounce) package dry taco seasoning mix 1 (15-ounce) can black beans, rinsed and drained 3/4 cup (3 ounces) shredded Mexican cheese blend, divided 6 (6-inch) tostadas (see Note) 2 scallions, sliced

1. In a large nonstick skillet, heat oil over medium heat. Add chicken and sauté 2 minutes, until browned. Add water and taco seasoning; reduce heat to low and simmer 5 minutes. Add black beans and simmer 2 more minutes; remove from heat.
2. Arrange tostadas on a serving platter; sprinkle evenly with cheese then top with chicken mixture and sprinkle with scallions. Serve immediately.