Cut chicken breasts on the bias so that they are somewhat even in height.
Place cut chicken breasts in a zip lock bag; seal and pound with a rolling pin or mallet to create uniform thickness of about ½ inch.
Open the zipper bag, and pour buttermilk into the bag so it coats the chicken; zip it up and place it in the fridge for an hour. (Using a bowl underneath protects against leaks in the fridge.)
Combine dredging ingredients in one bowl, and egg wash ingredients in another. Place a plate nearby, as this will serve as the "dredging station".
Pour oil into skillet or pot to 2 inches deep. Set to 350 degrees (which is roughly the medium to medium high setting on most stoves.) Be careful of little ones and handles as oil heats up to prevent injury.
Remove chicken from buttermilk bag. Roll in the flour mixture.
Dip in the egg wash mixture, and then roll back into the flour mixture to make sure
Work in batches so that chicken isn't crowded and it gets very crispy. it sticks. Stack onto a plate as you go.
Drain on a metal baking rack that is set over another baking sheet to catch the drips. Don't ever set fried chicken (or fried anything) directly on paper towels or other absorbent materials.
Spread mayonnaise onto the top and bottom sesame seed buns. Place chicken on the bottom bun, followed by shredded lettuce and top bun.