1. Adjust oven rack to middle position; heat oven to 250°F. Spread bread cubes in single layer on baking sheet; bake until thoroughly dried but not browned, about 30 minutes, stirring once halfway through baking time.

2. Meanwhile, heat butter in 12-inch skillet over medium-high heat; when foam subsides, add leek, celery, and mushrooms and cook, stirring occasionally, until vegetables begin to soften, about 4 minutes. Add garlic and continue to cook, stirring frequently, until vegetables begin to brown, 2 to 3 minutes. Stir in sage, thyme, and parsley and cook until fragrant, about 1 minute.

3. Whisk egg, broth, salt, and pepper in large bowl until combined. Add bread cubes and leek/mushroom mixture; toss gently until evenly moistened and combined. Set aside. Prepare Stuffed Roast Butterflied Chicken according to recipe (see related content), using stuffing when called for in step 3.

Enough for 1 butterflied chicken