Preheat oven to 400°F. Line a baking sheet with foil and spray lightly.
Mix panko, Parmesan, garlic powder, salt, and pepper in a bowl.
Dip tenders in egg, then coat with breadcrumb mix. Place on sheet; drizzle olive oil.
Bake 12–14 minutes until golden and 165°F inside.
Split buns, spoon marinara on bottoms, add a tender and half a mozzarella slice.
Close sliders, brush tops with melted butter, and bake 3–4 minutes more to melt cheese.
Sprinkle parsley if you want. Kids will dive in; I serve with carrot sticks.