MUSTARD-HERB Brine: Combine all ingredients except chicken in stockpot; bring to boil. Cool. Pour over chicken in full-hotel pans. Refrigerate 24 hours.
MOLASSES Mustard: Mix ingredients until well blended. Refrigerate until ready to use.
SEASONED Flour: Mix ingredients. Divide between 2 bowls; set aside.
CHICKEN: WHISK milk, mustard and seasonings until well blended. Remove chicken from Mustard-Herb Brine; discard brine. Dredge chicken in first bowl of Seasoned Flour; gently shake off excess. Dip chicken in milk mixture, then dredge in second bowl of Seasoned Flour. Place in single layer in parchment paper-lined sheet pans. Refrigerate until ready to use.
FOR each serving: Cook 1 chicken breast in 350ºF-deep fryer 7 to 8 min. or until done (165ºF).
SPREAD 1 bread slice with 1 Tbsp. Molasses Mustard; top with 1 lettuce leaf, 3 tomato slices, 3 onion rings and chicken. Drizzle with 1 Tbsp. Molasses Mustard. Serve with second bread slice.