Heat the peanut oil in a pressure cooker over med. Heat to about 400~F. In a small bowl, beat the egg and stir in the milk. In a separate bowl, combine the flour, sugar, pepper, and salt. Dip each piece of chicken in milk until it is fully moistened. Roll the moistened chicken in the flour mixture until completely coated. Drop all four chicken pieces into the hot oil and close the pressure cooker. When steam starts shooting through the pressure release, set the timer for 3-1/2 minutes. While the chicken is cooking, spread a coating of melted butter on the face of each bun. When the chicken is done, remove it from the oil and drain or blot on paper towels. Place two pickles on each bottom bun; add a chicken breast, then the top bun. To make a deluxe chicken sandwich, simply add two tomato slices and a leaf of lettuce. Mayonnaise also goes well on this sandwich-it is a side order at the restaurant.