Preheat your oven to 400F/200C.
In a small saucepan, put the pizza sauce and simmer it over low heat until it reduces to one cup. This usually takes about twenty minutes. Don’t skip this step; a watery sauce will ruin your dish.
While the sauce reduces, take the chicken breasts and trim off any excess fat. Cut each breast crosswise into two pieces for even cooking.
Next, place each piece inside a heavy plastic bag and use a meat mallet to pound the chicken until it's as thin as you can manage without shredding it apart. This makes for tender and juicy chicken.
Mix the Greek oregano and garlic powder in a small bowl. Sprinkle this mixture generously on both sides of your chicken pieces.
Heat the olive oil in the largest non-stick frying pan over medium-high heat. If your pan isn’t big enough, you may need to do this in two batches to avoid overcrowding.
Once the oil is hot, add the chicken pieces to the pan. Cook for one to two minutes on each side until the chicken is nicely browned but not fully cooked.
Choose a small glass casserole dish that will fit all the browned chicken pieces in a single layer. Arrange the chicken neatly in the dish.
Slice the Mozzarella and distribute the slices over the top of each piece of chicken, covering them mostly.
By now, your sauce should be reduced; spread it generously over the chicken. Use it all to ensure maximum flavor!
Top each piece with pepperoni slices, ensuring they’re placed to cover as much of the chicken as possible.
Finally, bake the casserole uncovered for about twenty-five to thirty minutes. You'll know it's done when the cheese has melted and started to brown, and the pepperoni is slightly crisped. Serve hot and enjoy!
This dish is excellent reheated in the microwave for a few minutes, although you might not have any leftovers!
