Spinach and Feta Stuffed Chicken

First I trimmed 4 large chicken breasts and then carefully made a pocket in each one.  This was really difficult; I cut too much in two of the six chicken breasts, but I only needed four.  For the stuffing, I used thawed, drained frozen spinach; it's really important to drain this well.  I mixed the spinach with equal parts feta cheese and sour cream.  The filling looked just like a spinach dip.  I divided the spinach filling into four equal parts and filled each chicken breast.  I seasoned all four chicken breasts and then seared them in olive oil in a skillet.  Once seared, I transferred the skillet to the oven to finish cooking.