Preheat oven to 375 degrees F. Line a large baking sheet pan with parchment paper.
Place chicken breasts on a cutting board, and slice 3 slits into each breast, about ¾ of the way, being careful not to cut through the breast.
Drizzle oil over breasts and rub into the slits with your fingers. Place onto sheet pan. Sprinkle with ½ teaspoon of salt and pepper. Set aside.
In a large bowl, combine the egg, spinach, ricotta, mozzarella and remaining ½ teaspoon of salt.
Evenly spoon spinach cheese mixture into each slit of the breasts. Place in the oven and cook for 35-40 minutes or until the internal temperature of each breast at its thickest part is 165 degrees F.
Place bacon onto another baking sheet pan and place in the oven to cook until crisp, about 20-25 minutes. Once the bacon is done, allow it to cool so you can handle it and chop into pieces.
When the chicken is done, sprinkle the chopped bacon over each breast and serve immediately.
Leftovers can be placed in an airtight container and stored in the refrigerator for up to 3 days.