*The previous night, place your chicken breasts to brine in a solution made of 1 tablespoon of salt for 2 cups of water. While this step is not absolutely mandatory, it creates a much juicier and tastier chicken and requires very little effort on your part. Trust me, it's totally worth it.
Preheat oven to 350F
In a bowl, add all the ingredients for the cheese filling and mix delicately with a spoon until well combined.
In a separate bowl, add the ingredients for the walnut crust and again, mix until well combined. Set aside.
With a sharp boning or petty knife, make an incision in each of the chicken breasts. Start at the thickest end and slowly work your way to the other end, while being careful not to let the blade go all the way through. You want to create a nice pocket for your cheese filling.
Insert one or two fingers in that pocket to stretch it a little bit and make sure that the passage is unobstructed all the way to the end.
Place the cheese filling in a pastry bag equipped with a large round tip and pipe it into the cavities. If you need to, pinch the openings between your fingers and give the breasts a gentle squeeze to evenly distribute the filling within the pocket.
Place the stuffed chicken breasts into a baking dish and pat them real dry, then press the walnut crust firmly over each of them.
Cover with aluminum foil and bake for 30 minutes; remove the foil and resume cooking for additional 25 minutes, basting from time to time.
If you feel the crust could use a little more coloring after the chicken is done cooking, set the oven to broil for 2-3 minutes.
Remove from oven, tent loosely with foil and let rest for at least 10 minutes, then slice on a diagonal and serve.