6 (4-oz.) boneless, skinless chicken thighs, cut into 1-in. pieces 1/2 teaspoon black pepper 1 1/2 teaspoons kosher salt, divided 1 tablespoon canola oil 3/4 cup uncooked long-grain white rice 1 (15-oz.) can black beans, drained and rinsed 1 1/4 cups cups chicken stock or water 1 cup fresh corn kernels (3 ears), or frozen, thawed, and drained corn 1 cup tomatillo salsa (such as Herdez Mild Salsa Verde), divided 6 ounces Cheddar cheese, shredded (about 1 1/2 cups), divided