Bring 8 cups water to a boil in a large saucepan. Sprinkle chicken with salt and black pepper and place into the boiling water. Reduce heat to medium-low; simmer until chicken is no longer pink inside, about 20 minutes. Remove chicken and chop. Reserve water in saucepan.
Stir potatoes, carrots, celery, onion, chicken bouillon cubes, and bay leaves into the water and bring back to a boil. Reduce heat to low and simmer until vegetables are tender, 15 to 20 minutes. Return chicken to the pot.
Preheat oven to 400 degrees F (200 degrees C).
Whisk cornstarch with 3 tablespoons water in a small bowl until smooth and stir mixture into the simmering soup until soup has thickened, about 1 minute.
Pour soup into a 9x9-inch casserole dish and top with biscuits. Melt butter in a small saucepan. Stir garlic powder, onion powder, and parsley into melted butter. Brush biscuits with seasoned butter.
Bake in the preheated oven until biscuits are golden brown, 10 to 12 minutes.