PRETZEL Crumb Breading: Pulse pretzels in food processor until evenly ground. Add parsley and garlic; pulse until well blended. Set aside.
CHICKEN: POUR beer over chicken in non-reactive dish; turn to evenly coat both sides of each breast. Refrigerate at least 30 min. or up to 24 hours to marinate. Remove chicken from marinade; discard marinade. Pat chicken dry with paper towels; season with salt and pepper. Pound to 1/2-inch thickness. Brush each breast with 1 Tbsp. mustard; dredge in Pretzel Crumb Breading. Refrigerate until ready to serve.
FOR each serving: Heat 2 Tbsp. oil in small skillet on medium heat. Add 1 chicken breast; cook 2 min. on each side or until browned on both sides. Transfer to parchment-lined half sheet pan; bake in 350ºF standard oven until done (165ºF). Immediately top with 1 cheese slice.
PLACE 2 tomato slices on bottom half of roll; top with 1 lettuce leaf and chicken. Spread top half of roll with 1 Tbsp. mustard; place over sandwich.