Boil the potatoes in salted water for 15 minutes until a knife slides through easily, then drain and mash with the butter, milk and salt.
Heat the frying oil to 350°F, dip the chicken pieces in beaten egg, and press them into the seasoned flour.
Fry the chicken in two batches for 4 to 6 minutes until crisp and 165°F inside, then drain on a rack.
Warm the corn and gravy in separate saucepans until steaming, thinning the gravy with 2 tablespoons water if it does not pour.
Divide the potatoes among 4 bowls and top each with corn, chicken and a measured ladle of gravy.