Wash and dry produce. 

Halve tomato lengthwise; thinly slice crosswise into half-moons. Season all over with salt and pepper. 

In a shallow dish, combine panko and Italian Seasoning.

Pat chicken* dry with paper towels; place between two large pieces of plastic wrap. Pound with a mallet or rolling pin until about ½ inch thick. Season all over with salt and pepper.

Brush chicken all over with sour cream. Working one piece at a time, press chicken into seasoned panko until fully coated on both sides.

Heat a ⅓-inch layer of oil in a large, heavy-bottomed pan over medium-high heat. Once oil is shimmering and hot enough that a pinch of panko sizzles when added to the pan, add coated chicken in a single layer. Cook until panko is golden brown and chicken is cooked through, 4-6 minutes per side (for 4 servings, you may need to work in batches). 

Transfer to a paper-towel-lined plate and immediately season with salt.

While chicken cooks, thinly slice mozzarella into rounds.

In a medium bowl, whisk together ½ TBSP vinegar (1 TBSP for 4 servings) and a drizzle of olive oil; season with salt and pepper. (Save remaining vinegar for another use.)

Add arugula and half the tomato to bowl with dressing; toss to combine.

Slice baguettes lengthwise, stopping before you cut all the way through. Toast until golden brown.

Fill baguettes with chicken, mozzarella, prosciutto, and remaining tomato. 

Halve subs on a diagonal. 

Divide subs and salad between plates. Serve.