Step 1

Preheat oven to 400F/200C.

Step 2

Put the pizza sauce in a small saucepan and simmer over low heat until it's reduced to one cup, about 20 minutes.  Don't skip this step or the dish will be watery.

Step 3

While the sauce reduces, trim the chicken breasts and cut each one crosswise to make two same-size pieces.  Put chicken pieces one at a time inside a heavy plastic bag and use a meat mallet (affiliate link) (or something heavy) to pound the chicken until it's as thin as you can get it without it shredding apart.  (Don't worry if some pieces break apart a little.)

Step 4

Mix the Greek Oregano (affiliate link) and garlic powder in a little bowl and then sprinkle both sides of each piece of chicken with the mixture.

Step 5

Heat the olive oil over medium-high heat in the largest non-stick frying pan you have (you may have to do this in 2 batches if your pan isn't big enough.) Add the chicken pieces and cook 1-2 minutes on each side, just long enough to brown the chicken but not long enough to cook it through.

Step 6

Choose the smallest glass casserole dish you have that will fit all the browned chicken pieces, and lay the chicken in the dish in a single layer.  Cut the Mozzarella into slices and cut the slices as needed to make enough pieces to mostly cover the top of each piece of chicken.

Step 7

By now the sauce should be nicely reduced, so spread sauce over the top of each chicken breast.  (Use it all.)  Top each piece with sliced Mozzarella and pepperoni slices, covering the top of each piece of chicken as much as you can.

Step 8

Bake uncovered about 25-30 minutes, or until the cheese is melted and starting to brown and the pepperoni is slightly crisped.  (Some pieces of pepperoni will slice off the chicken, try not to obsess about that like I did.)  Serve hot.

Step 9

This was great reheated in the microwave for a few minutes, although you might not have any left!