Preheat the oven to 350˚F and add olive oil to a large oven-safe skillet and set aside.
Slice the chicken breast in half starting from the side, but do not cut all the way through, you want to make a pocket for the filling.
To make the stuffing, begin by microwaving the chopped spinach in a large bowl for 90 seconds to wilt the spinach.
Remove the spinach from the microwave and stir in the cheeses, sour cream, cream cheese, and seasonings until well combined. Stuff equal parts of the spinach mixture into the prepared chicken breasts and place in the prepared skillet.
Sear the chicken over medium-high heat on both sides until golden brown. Transfer the chicken to the oven and bake for 30 to 40 minutes or until the chicken reaches an internal temperature of 165 degrees F.