Heat olive oil and butter in saute pan over medium heat. Add leeks and cook for 4 minutes.
Add 1 tablespoon each of rosemary and thyme, cook one minute more.
Season with 1/2 teaspoon each of salt and pepper. Transfer to bowl; let cool.
Using a knife with a sharp, pointed blade, cut a pocket into the center of each chicken breast by inserting the tip into the thickest part of the breast, being careful not to cut the whole way through. Place 2 tablespoons of leek mixture into each pocket.
Make bread crumbs by placing bread into food processor fitted with metal blade. Add remaining herbs, salt and pepper.
Spread 1 teaspoon mustard over top of stuffed chicken breast.
Cover with herbed bread crumbs, pressing gently to adhere.
Place chicken breasts in roasting pan, bread crumb side up.
Pour chicken stock and wine into pan around chicken.
Cover with foil, bake for 25 minutes. Remove foil and bake 10 minutes more. Internal temperature should reach 165 degrees.