Slice chicken breasts in half horizontally and pound to an even thickness.
Set up three separate coating stations: one with flour, one with beaten eggs, and one with panko breadcrumbs.
Coat each chicken piece in flour, then dip in the beaten eggs, and finally cover in panko breadcrumbs.
Heat vegetable oil in a large skillet over medium-high heat.
Fry the chicken for 4-5 minutes on each side until golden brown.
Mix mayonnaise with dill and lemon juice for the sauce.
Toast brioche buns until golden brown.
Assemble sandwiches with dill mayo, lettuce, fried chicken, and pickles.