Season the thin chicken breasts evenly with Italian seasoning, garlic powder, and salt.
Heat the olive oil in a large skillet over medium heat.
Once the oil is hot, place the chicken in a single layer in the skillet.
Cook the chicken for 3 minutes per side without moving it, allowing a golden sear to form.
If the skillet is not large enough to hold all the chicken in one layer, cook the chicken in 2 to 3 batches to avoid overcrowding.
Transfer the seared chicken to a plate and set aside.
Add the chopped pepperoni and pressed garlic to the same skillet.
Cook for 30 to 60 seconds, stirring frequently, until the garlic is fragrant and the pepperoni begins to release its flavor.
Add the crushed tomatoes, Italian seasoning, and salt to the skillet.
Stir well and scrape the bottom of the skillet to loosen any browned bits from the chicken.
Slowly stir in the heavy cream until fully incorporated into the tomato sauce.
Add the parmesan cheese and stir until combined.
Return the seared chicken and any accumulated juices to the skillet.
Spoon the sauce over the chicken.
Simmer until the chicken is fully cooked and reaches an internal temperature of 165°F.
Turn off the heat.
Sprinkle the mozzarella cheese evenly over the chicken.
Cover the skillet and allow the cheese to melt for 4 to 5 minutes.
Garnish with freshly chopped parsley, if desired.
Serve warm with pasta, rice, garlic bread, roasted vegetables, salad, zucchini noodles, or crusty bread.