Chicken Cordon Bleu Sandwiches

4 chicken cutlets
1.5 T olive oil plus more for drizzling
Kosher salt and fresh pepper
4 slices black forest ham
8 slices smoked mozzarella
1 baguette
3 T unsalted butter, soft
3 T Dijon mustard
1 bunch watercress or arugula (remove tough stems)

Preheat broiler. Line baking sheet with foil. Place chicken in the center. Brush chicken with 1 T oil and season with salt and pepper. Broil, rotating the baking sheet as needed so the chicken cooks evenly, until lightly browned, 2-3mins. Flip the chicken and continue to broil until cooked through 2-3 more minutes.
Remove the baking sheet from the oven and top each piece of chicken with 1 slice ham and 2 slices mozzarella. Broil until the cheese melts. Season with salt and drizzle with olive oil.
Meanwhile, cut the baguette crosswise into 4 equal parts then split open. Spread the bottom halves with butter and the top with mustard. Toss watercress with the remaining 1/2 T olive oil and season with salt and pepper. Sandwich the chicken and watercress between halves.
Serve