• 2 pounds Yukon Gold potatoes , peeled and cut lengthwise into 6 wedges each
• 6 tablespoons extra-virgin olive oil
• Salt and freshly ground pepper
• 1 1/2 pounds assorted mushrooms , such as shiitake, oyster, cremini, portobello or white button, sliced or quartered
• 1/4 cup finely chopped shallots
• 2 cloves garlic , coarsely chopped
• 4 (7- to 8-ounce) boneless skinless chicken breast halves, rinsed and patted dry
• 1/3 cup grainy mustard , such as moutarde de Meaux
• 3 tablespoons chopped fresh herbs , such as tarragon, chives, or thyme, or a combination

Position a rack in the center of the oven and preheat to 400°F. Toss the potatoes with 2 tablespoons of the olive oil in a large bowl and season to taste with salt and pepper. Spread in a large roasting pan. Roast, turning occasionally, until they are just brown and almost tender, about 45 minutes. Remove from the oven and set aside. Reduce the oven temperature to 350°F.

Meanwhile, heat 2 tablespoons of olive oil in a large nonstick skillet over high heat. Add the mushrooms and cook until lightly browned, about 7 minutes. Season to taste with salt and pepper. Add the chopped shallots and garlic. Cook, stirring occasionally, until the shallots are softened, about 2 minutes. Stir into the potatoes.

Heat the remaining 2 tablespoons of olive oil in a large skillet over medium-high heat. Season the chicken with salt and pepper. Add to the skillet and cook, turning once, until golden brown on both sides, about 8 minutes.

Arrange the browned chicken breasts on top of the potatoes and mushrooms. In a small bowl, combine the mustard, herbs, and salt and pepper to taste. Spread the mixture evenly over the chicken breasts. Bake until the breasts show no sign of pink when pierced in the center, 15 to 20 minutes.

Spoon the potatoes and mushrooms onto dinner plates, and top with the chicken breasts. Serve hot.