In a large skillet over medium heat, add 1 tablespoon olive oil.
Add onion and cook for about 8 minutes. Don’t forget to stir occasionally.
Add spinach and cook for 1 minute. Remove pan from heat. Add feta and black olives and mix everything well to combine. Set it aside.
Prep the chicken:
Cut the chicken into 8 pieces and pound all the four pieces until they are thin. Season chicken with salt and pepper on both sides. Put 1 ½ tablespoon of the spinach mixture in the middle of the chicken and roll it up. Secure together using toothpicks, if needed. Repeat the process for all the chicken pieces.
Put ½ cup of the tomato sauce on the bottom of a greased baking dish and set it aside.
In a skillet, sauté the chicken breast in oil until golden brown. Then transfer the chicken to the baking dish.
Cover evenly with remaining tomato sauce and bake for 25 to 30 minutes until the chicken gets to an internal temperature of 165°F degrees.
Remove chicken from the oven, top with mozzarella cheese and bake for more 2 minutes. Before serving top with fresh parsley.
Video
Notes
Make sure to pound the chicken into even thickness so they all cook through at the same time.
Since spinach wilts as they cook, it's best to cook them before adding them to the chicken.
I recommend shredding your own mozzarella as pre-shredded cheese tends to not melt as smoothly.
To store: Store leftover chicken breasts in an airtight container for up to 4 days in the fridge.
To reheat: You can reheat in the microwave when ready to eat. You can also eat chicken cold.
To freeze: You can freeze stuffed chicken breasts in a freezer-safe bag or container for up to 3 months.