Preheat oven to 400 degrees.
Place the chicken thighs in a 9 by 13 baking pan.
In a bowl, mix together the mayo, parmesan, Italian seasoning, garlic and onion powder.
Evenly spread this over the chicken.
Bake the chicken for 30 minutes until the top is slightly browned.
Remove from oven and top with mozzarella cheese and pepperoni.
Bake for another 5 minutes or until cheese is melted.
Make Ahead: Follow recipe to step 5. Cool completely then cover with plastic wrap. Freeze or refrigerate until the night you want to serve. Then reheat at 350 for 30 minutes and top with cheese and pepperoni.