Preheat the oven to 375°F degrees.

Slice a pocket into the side of the chicken breast lengthwise to create a pocket for stuffing.

Season the inside and outside of the chicken with salt and pepper.

Heat a skillet over medium heat, add the oil, onions, and prosciutto; sauté until golden, 3 to 4 minutes. Add the sage and pear, season with a pinch of salt and cook for 3 to 4 minutes or until translucent.

Remove from heat, and add the arugula. Set aside to cool a few minutes.

Divide the stuffing and fill each breast with the pear filling and brie. Cut cooking twine and tie the chicken breast closed with 3 pieces for each.

Heat an oven-proof skillet over medium-high heat and lightly spray with cooking spray. Carefully sear the outside of the chicken on all sides except where the stuffing is until golden brown.

Set the chicken cut side up and place the skillet in the oven (if you don't have an oven-proof skillet place in a baking pan). Cover the skillet tightly with foil and cook for 23 to 25 minutes, or until the chicken is cooked through.

To serve, cut each breast in half and serve.