Pound each chicken breast to 1/4 inch thickness.
Sprinkle each breast with salt and pepper then dredge both sides in flour, dip in egg and coat with panko crumbs, pressing to make sure crumbs coat the chicken well.
In a large saute pan, heat 2 Tbsp. butter and 2 Tbsp. olive oil over medium low heat. Add the chicken and saute on each side for 3 minutes until cooked through, adding more butter and olive oil as needed.
Remove chicken from pan and top each with some arugula, tomatoes and fresh mozzarella. Drizzle with some balsamic vinaigrette and sprinkle with salt and freshly ground pepper to taste.