Preheat oven to 400°F.
Heat 1 tsp oil in a large non stick skillet over medium-high heat. Add mushrooms and shallot; cook 6 minutes. Add spinach and parsley; cook 1 minute. Transfer to a bowl. Stir in bread crumbs, egg white, 1/4 tsp salt, and 1/4 tsp pepper.
Sprinkle chicken with 1/4 tsp each salt and pepper. Insert a clean, sharp knife into the thickest side of each chicken breast. Make a 2 inch slit. Cut to, but not through the opposite side. Holding the knife blade parallel to the cutting board, guide the blade around the inside, creating a pocket. Be careful not to cut through the sides.
Divide the mushroom mixture between the 4 breasts. Stuff into the pockets.
Wipe the pan clean with paper towels. Heat 2 tsp oil in pan over medium heat; add chicken. Cook 5 minutes, turning frequently, until browned. Transfer chicken to a baking sheet lined with foil. Bake for 13 minutes or until done at 400°F.
Add wine to pan; cook 2 minutes over medium heat, scraping pan to loosen bits.
Whisk together cream sauce mix, broth, and milk; add to pan. Bring to a boil; reduce heat, and simmer 1 minute. Stir in lemon juice.
Spoon sauce onto serving plates; arrange chicken over sauce.
Yields 4 servings: 1 breast and about 1/4 cup sauce).