Preheat oven to 400°F (200°C)
Using a meat mallet, lightly pound chicken breasts to an even thickness, about 1/4 inch
In separate bowls, set up a breading station: flour in one bowl, beaten eggs in the second, and seasoned panko in the third
Season one side of the chicken breasts with garlic powder, oregano, salt, and pepper
Dredge chicken breasts in flour, shaking off excess. Next, dip in the egg, then press into the panko breadcrumbs to coat both sides
Place breaded chicken breasts on a baking sheet and bake for 12 to 15 minutes until golden and cooked through
Meanwhile, lightly toast the slider buns, open-side-up, on the same baking sheet during the last 2 minutes of baking
To assemble, spread a generous amount of marinara on the bottom halves of the buns, top with a chicken breast, add mozzarella cheese, sprinkle Parmesan cheese, and cover with the top of the bun
Place the assembled sliders back on the baking sheet and return to the oven for 2 to 3 minutes, allowing the cheese to melt and the buns to slightly crisp