Heat your oven to 400ºF and set out a large sheet pan.Using a sharp knife, carefully cut each chicken breast into two equal cutlets by slicing horizontally through the breast. Set aside.
Melt the butter in a large skillet over medium heat and add in the panko. Season with salt and pepper and cook, stirring frequently, until golden brown. Transfer the panko into a shallow dish and stir in the Parmesan, garlic powder, and 2 teaspoons of the Italian seasoning. Allow it to cool to room temperature.
Meanwhile, in a separate shallow dish, whisk together the eggs and mayonnaise and season with salt and pepper. Working with one piece of chicken at a time, dunk into the egg mixture, then press into the panko to coat and transfer to the prepared sheet pan.
Add the tomatoes and garlic cloves to a large bowl along with the remaining teaspoon of Italian seasoning. Add in the olive oil, season with salt and pepper, and toss to combine. Dump the tomatoes onto the sheet pan between the breaded chicken and bake for 18 to 20 minutes or until the chicken is cooked through to 165ºF and the tomatoes are starting to burst.
Remove the sheet pan from the oven and top each piece of chicken with the mozzarella cheese. Turn the broiler onto high, return the sheet pan to the oven, and broil just until the cheese has melted.
Tear the basil overtop and serve immediately with a salad and/or bread on the side.
