Pound chicken to ½-inch thickness. Season both sides with salt, pepper, garlic powder, oregano, and basil.
Set up 3 bowls: flour, beaten egg, and breadcrumbs mixed with Parmesan. Dredge chicken in flour, dip in egg, then coat in breadcrumbs.
Heat olive oil in a skillet. Cook chicken 4–5 minutes per side until golden and cooked through. Let rest, then slice into strips.
Spread marinara on bread slices. Add chicken strips, more marinara, mozzarella, and Parmesan. Top with another slice of bread.
Butter the outsides. Grill 3–4 minutes per side in a clean skillet until golden and cheese melts.
Slice and serve warm with extra marinara for dipping.