On a cutting board, salt and pepper both sides of each chicken breast with approximately ½ teaspoon salt and ½ teaspoon pepper, per side.
Slice each chicken breast horizontally along the side to create a pocket for the filling.
Stuff each breast with approximately one third of mozzarella cheese, one tablespoon pesto and four sundried tomatoes. If the chicken breast does not close fully with the filling, try securing with a wooden toothpick.
Heat oil in a skillet over medium heat.
Pan fry for about 5-8 minutes, per side, depending on the size of the chicken breasts, until the cheese is melted and the chicken is cooked through. Serve warm.