Grind the chicken breasts using a meat grinder food processor. If you have skins, you should add them too. Transfer to a medium bowl.
Add the remaining patty ingredients and mix vigorously for at least 2 minutes minute. I like wearing plastic gloves and really getting into the meat. This will give the patties a firmer and bouncier texture when cooked.
Line a baking sheet with parchment paper. Divide the chicken mixture into six equal portions and shape into ⅓-inch thick patties. Arrange the patties on the baking sheet and freeze for 1 hour to firm up. This will make them much easier to bread.
In a shallow dish, whisk the flour and eggs into a smooth paste. It should have the consistency of a thick pancake batter. Add extra flour or water as needed.
In a food processor, blend the breadcrumbs into a fine powder. This should take about ten 5-second pulses. Transfer to a shallow dish.
Take one chicken patty at a time, coat it in the wet batter, and then press it into the breadcrumbs. Set it aside and repeat with the remaining patties.
Heat about 1 inch of oil to 350°F. Fry 2-3 patties at a time for 4-6 minutes or until the inside reaches an internal temperature of 165°F. Transfer to a wire rack to drain excess oil.
Now it is time to assemble the burgers. First, toast the hamburger buns so they are slightly golden. For each sandwich, spread two teaspoons of mayo on each bun, place a chicken patty on the bottom bun, add shredded lettuce on the top bun, and then combine the two buns. Enjoy!