Ain't nothing wrong with bringing more Dijon into your life. Here, you get to sauce a chicken breast with a luxurious mix of robust Dijon, cream, and rich butter. But mustard isn't the only star of this dish: You'll never eat zucchini the same way after savoring it in this gratin, made with nutty Parmesan and jammy sun-dried tomatoes, and topped with crispy fried onions.