2 tablespoons olive oil
1 yellow onion, diced
2 garlic cloves, minced
1 (28-ounce) can of crushed or pureed tomatoes, preferably San Marzano
2 teaspoons kosher salt, divided, plus more as needed
1 teaspoon pepper, divided, plus more as needed
2 large eggs
1 cup panko
3 tablespoons finely grated Parmesan, plus 4 tablespoons
2 boneless, skinless chicken breasts, halved horizontally (like you’re slicing a layer cake into two layers), then pounded to 1/2-inch thick (so you have 4 roughly 5-ish-ounce cutlets total, 1/2-inch thick each)
2 tablespoons avocado oil (or other high-heat-friendly neutral oil)
1/2 cup grated low-moisture, whole-milk mozzarella
Make the sauce. Add 2 tablespoons olive oil to a pot set over medium heat, then add the onions. Cook until the onions are just becoming translucent, then add the garlic. Continue to sauté another 1 to 2 minutes, until the garlic is fragrant.
Add tomatoes, 1 teaspoon salt, and 1/2 teaspoon pepper, and stir to combine. Cook over medium-low heat for about 15 minutes, until it’s thickened and tastes rich and a little sweet. Add more salt and pepper to taste.
Meanwhile, while the sauce is cooking down, get a large bowl, and two plates. In the large bowl, lightly beat the eggs until there are no big streaks of egg white visible.
On one of the plates, sprinkle the panko, 3 tablespoons Parmesan, 1 teaspoon of salt, and 1/2 teaspoon of pepper, and use a fork to mix thoroughly.
One at a time, take your chicken pieces and dredge them through the egg, letting any excess drip off back into the bowl. Once dredged in egg, press each side of the chicken firmly to the panko-Parmesan mixture to coat. Set aside on the second, clean plate.
Turn on your broiler. (If your broiler is on the inside-top of your actual oven, before you turn it on, move your highest oven shelf as close as possible to the broiler, and use this top shelf for the remainder of the steps). Place your largest cast iron skillet under your broiler. Let it heat up under there for 5 minutes. Use this time to mix together the mozzarella and remaining 4 tablespoons of Parmesan, and set that aside.
Using oven mitts (it’ll be very hot!), take out the skillet. Add the avocado oil and the four chicken pieces—spaced out, in a single layer—into the pan.
Place the pan under broiler. Broil for 3 to 4 minutes, until the tops of the cutlets are crispy and golden brown. (Peek after 3 minutes to avoid burning. If, after 4 minutes, the tops still aren’t getting golden, leave it for another minute or so.)
Remove the skillet from the broiler. Use a spatula to flip over the chicken, and top each piece with several spoonfuls of sauce, and a heavy sprinkling of mozzarella and Parmesan. Place back under broiler for another 2 minutes until cheese is bubbling and dotted with brown spots.
Remove from the broiler. Serve hot, preferably with big hunks of buttered bread.