A quick and flavorful stuffed chicken

I was starting to feel like I was accumulating a few too many leftovers from a variety of different meals and dishes when I whipped together last night's dinner. There is no worse feeling than tossing half a bag of wilted spinach or a nice chunk of cheese that got moldy when you know damn well that you could have done something amazing with it.

Enter my fridge and pantry. Here's what needed some quick love:

3 frozen chicken breasts
1/4 bag of fresh arugula
1/2 ball fresh mozzerella cheese
1/4 bag of freshly grated parmesan
breadcrumbs
spices
1/2 small yellow onion

Here's what I did with it:

Thaw the chicken breast overnight in the refrigerator. If it is still frozen at the time you want to cook, run it under hot water for 5 minutes.
Slice the chicken breast down the middle, being careful not to cut the whole way through.
Place the chicken on a greased baking sheet.
Using a new knife and a new cutting board (nobody likes contamination), slice the fresh mozzerella into crescent moon shapes (cut each slice in half). Basically, it needs to be small enough to fit in the chicken.
Cut the onion into small chunks, about the size of a clove of garlic.
Place 2 to 3 slices of mozzerella in each chicken breast. Stuff a small handful of arugula in the chicken as well, being sure that none of the leaves spill out (they will burn and shrivel quickly in the oven if they are exposed to the direct heat).
Season the tops of the chicken with crushed black pepper, salt, garlic powder and dried basil.
Lightly dust the tops of each chicken breast with about a teaspoon of breadcrumbs and a teaspoon of the grated parmesan.
Place the onion chucks on the baking sheet all around the chicken (this will infuse a yummy flavor and leaves it up to you if you want to eat the onions or not. I devoured them happily and mixed some in my side dishes).
Drizzle olive oil over the chicken and the onions to crisp everything up.
Bake at 350 degrees for 20-25 minutes until the chicken is cooked through.
Serve alongside brown rice and vegetables of your choice!

This was really delicious and all the different flavor profiles played together really well. It was packed with peppery arugla, tart spices, and the mozzerella gave everything a smooth finish. This entire dish was completely unprepared -- I just tried to get inspired by what I had left over.

What is your most impressive left over dish?! How do you ramp up plain, old chicken into something more gourmet?