Deconstructing a familiar classic is always fun. Here the anchovy and Parmesan dressing becomes a rub for grilled chicken and the crunch comes from a crisp panko crust instead of croutons. The anchovy adds a briny, savory depth to the chicken that isn’t fishy, but you can omit for a version that’s more kid-friendly. Instead of shredded lettuce, we grill romaine hearts whole for more of a centerpiece, knife-and-fork feel. Most grill pans are made of cast-iron and are oven-safe. If yours is not, or your pan is missing a handle, use a cast-iron skillet instead.
Combine mustard, half of cheese, and anchovy in a bowl. Heat a grill pan over medium-high; coat with cooking spray. Sprinkle chicken with salt and pepper; add to pan, and cook 4 minutes. Turn, brush with mustard mixture, top with panko, and coat with cooking spray. Place pan in oven; broil 7 minutes or until chicken is done. Let stand 5 minutes. Cut into slices.
Return pan to medium-high. Brush cut sides of lettuce with 1 tablespoon oil. Grill lettuce, 2 halves at a time, for 2 minutes.
Place 1 chicken breast and 1/2 lettuce heart on each of 4 plates. Top lettuce evenly with remaining 1 tablespoon oil, juice, and remaining 3 tablespoons cheese.