Preheat oven to 425°F. Grease a 9x13-inch baking dish with nonstick cooking spray.
Pat chicken dry with paper towels. If needed, lightly pound chicken breasts to an even thickness. Arrange in the baking dish and season both sides with salt and pepper.
In a small bowl, stir together mayo and parmesan. Spread the mixture evenly over the top of each chicken breast.
Sprinkle panko and Italian seasoning evenly over the mayo-parmesan layer.
Bake uncovered for 18 to 22 minutes, or until the internal temperature reaches 165°F and the topping is golden brown. If needed, broil for the last 1 to 2 minutes for extra browning.
Let the chicken rest for 5 minutes. Garnish with fresh parsley and serve.
Notes
Pound the chicken first. Even thickness ensures the breasts cook at the same rate. Thick spots stay undercooked while thin edges dry out. A quick pound before baking fixes both.
Full-fat mayo is best. Light mayo has more water content, which can make the coating slide or steam. Full-fat gives you better flavor and a better crust.
Parmesan tip. Canned grated parmesan works well here. Freshly grated off the block is great too, but the finely grated canned variety melts into the coating nicely.
Breadcrumb swap. No panko? Regular breadcrumbs work, though the topping won't be quite as crunchy. For gluten-free, try crushed pork rinds or almond flour.
Chicken thighs. Boneless, skinless thighs are a great swap. Skip the pounding step and bake for 22 to 26 minutes, or until 165°F internal temperature.
Air fryer. Preheat to 375°F and cook in a single layer for 15 to 18 minutes, or until the internal temperature reaches 165°F.
Make-ahead. Assemble in the baking dish, cover, and refrigerate for up to 24 hours before baking.
Storage. Refrigerate leftovers in an airtight container for up to 4 days. Reheat in a 350°F oven for about 10 minutes or in the air fryer to keep the topping crispy.