1. Prepare stuffing mix according to package directions, and let cool. Stir in egg and pecans.
2. Butterfly chicken breasts by making a lengthwise cut in 1 side, cutting to but not through the opposite side; unfold. Spoon stuffing mixture evenly down center of one side of each butterflied chicken breast; fold opposite side over stuffing, and place in a lightly greased baking dish. Stir together 3 Tbsp. olive oil and chopped rosemary; brush evenly over chicken. Sprinkle chicken evenly with salt, pepper, and Parmesan cheese.
3. Bake chicken, uncovered, at 400° for 20 minutes or until done.
4. Sauté mushrooms and onions in remaining 1 Tbsp. oil in a large skillet over medium-high heat 5 minutes or until tender; stir in soup and chicken broth. Reduce heat, and simmer, stirring often, 5 minutes or until thoroughly heated. Spoon mushroom mixture evenly over chicken; garnish, if desired.
Note: For testing purposes only, we used Stove Top Cornbread Stuffing Mix.