Preheat the oven to 350 degrees. Line a baking sheet with parchment paper. Butter the slider rolls and place on the prepared baking sheet.
Make a breading assembly line with three separate dishes. Pour the flour in a dish then season with garlic powder, sea salt, and freshly cracked pepper, to taste; mix until well combined. Beat the egg and milk together in a bowl; whisk well. Combine the Italian panko crumbs together in a separate dish with the parmesan; mix well.
Prepare the chicken by slicing the chicken breasts in half lengthwise (place your hand on the chicken breast then carefully cut horizontally) then cut each portion in half.
Dredge the chicken by dipping each piece of chicken completely in the flour, followed by the egg, and lastly the Panko/Parmesan mixture. Set on a plate and repeat with the remaining pieces of chicken. Place the plate in the refrigerator for 30 minutes. Side Note: Don’t skip this step because it helps the breading stay adhered to the chicken.
Cook the chicken by melting 1 tablespoon of butter and 1 tablespoon of olive oil together in a large skillet over medium-high heat. Add the chicken to the HOT skillet and cook for 4-5 minutes, or until golden brown. Flip the chicken over and continue to cook for another 3-4 minutes, or until golden brown and cooked through.
Toast the prepared slider buns while the chicken is cooking, by placing the baking sheet in the preheated oven and cook for 4-5 minutes, or until toasted and golden. Remove from the oven and place the sliders on a serving plate.
Finish the chicken by placing a wire rack on the same baking sheet then place the cooked chicken on top. Spoon some marinara on each piece of chicken followed by a slice of mozzarella cheese. Place into the oven and bake for 3-4 minutes, or until the cheese is melted and gooey. Remove from the oven.
To serve, slather a bit of warmed marinara sauce on the bottom bun, if desired, then top with the chicken. Sprinkle some chopped basil on top followed by the remaining toasted bun. Serve immediately. Enjoy.