Place chicken breasts in a saucepan with enough water to cover; bring to boil and cook chicken until until no longer pink in the center and the juices run clear, about 10 minutes. Remove chicken to a cutting board to cool; cut into chunks.
Stir cream of chicken soup, milk, cornstarch, and garlic powder together in a pot over medium heat; season with salt and pepper. Stir chicken chunks into soup mixture; cook, stirring occasionally, until hot and the soup thickens, about 30 minutes.
Divide biscuit pieces among 6 bowls. Ladle chicken and sauce over biscuits to serve.