Preheat oven to 400degF.
Add sauce ingredients to a sauce pan over medium heat. Bring just to a bubble then reduce to low to simmer while preparing the rest of the meal.
Set up your dredging station. Tray one - 2 cups flour, and 1 teaspoon garlic powder. Tray two - egg, salt, pepper and remaining garlic powder. Tray three - breadcrumbs, parmesan cheese, and remaining flour. Bread chicken by thoroughly coating each piece in each tray.
Add enough oil to a large frying pan for ½ inch deep over medium-high heat. Once oil is around 350degF. Begin frying chicken, 2 minutes on each side then remove to baking rack over parchment paper covered baking sheet. Once all are fried, put in oven for 10 minutes.
Combine oil, vinegar, lemon juice, salt and pepper. Pour over arugula and toss to coat.
Begin toasting sourdough bread.
Remove chicken from oven and add ladle portion of red sauce over each piece. Place 2 slices of mozzarella atop each piece of chicken. Return to oven and bake another 10 minutes.
Build the sandwich, starting with toasted sourdough bread, smear with red sauce, add piece of chicken then top with portion of arugula and another piece of toasted sourdough. Secure with long toothpicks and cut in half to serve.