- 1 3½- to 4-pound chicken(s), spatchcocked, rinsed and patted dry with paper towels
- Kosher salt and freshly ground black pepper
- 2 tablespoons unsalted butter, softened to room temperature
- 1½ tablespoons chopped fresh thyme
- 1 tablespoon balsamic vinegar
- 10 ounces white button mushrooms, left whole, or large mushrooms, quartered
- ½ pound good crusty bread (like a baguette or a country bread), cut into 1-inch cubes
- 1 fennel bulb, trimmed of fronds and cut into ½-inch pieces
- 8 oil-packed sun-dried tomatoes, cut in half
- 4 cloves garlic, smashed
- Sprinkle 2½ teaspoons salt and ½ teaspoon black pepper all over each chicken, including the cavity. Place a rack in a pan, put the chicken on top, and let sit for up to 24 hours, uncovered, in the refrigerator. (If you’ve brined the chicken, skip this step. Just sprinkle the bird with ½ teaspoon salt and ½ teaspoon black pepper and proceed with the rest of the recipe.)
- Preheat the oven to 425°F. Set an oven rack to the middle position. In a small bowl, mix the butter with half the thyme and all of the vinegar. Using a brush, spread the butter between the skin and the breast meat, taking care not to rip the skin, then brush the remaining butter allover the bird, including the cavity.
- In a large bowl, toss the mushrooms, bread, fennel, sun-dried tomatoes, and garlic with the remaining thyme, 1 teaspoon salt, and ½ teaspoon pepper. Scatter this mixture over the bottom of the roasting pan. Set the chicken on top, skin side up. Roast the chicken until it’s nicely browned all over and an instant-read thermometer inserted into the thickest part of the thigh registers 165° to 170°F, about 40 minutes.
- Transfer the chicken to a cutting board and let rest for 10 minutes. Meanwhile, return the pan to the oven for 10 minutes to brown and crisp the top of the dressing. Carve the chicken, drizzle with any juices accumulated on the cutting board, and serve with the dressing.