Autumn Harvest Stuffing

INGREDIENTS

• 1 (1-pound) loaf rustic white bread, crusts removed, and cut into 1-inch cubes
• 1 small butternut squash, peeled, seeded, and cut into 1/2-inch pieces
• 6 tablespoons olive oil
• Coarse salt and freshly ground pepper
• 1/2 cup thinly sliced shallots
• 2 ribs celery, chopped
• 1 small leek, white part only, chopped
• 4 cups cleaned, dried, stemmed, and torn mustard greens
• 12 ounces cremini mushrooms, trimmed and quartered
• 1 tablespoon chopped fresh sage
• 3 tablespoons fresh flat-leaf parsley, chopped
• 2 teaspoons fresh thyme
• 2 1/4 cups low-sodium store-bought chicken broth
• 1/4 cup (1/2 stick) unsalted butter, plus more for baking dish, if using