Preheat the oven to 425°F.

Stir the softened butter and olive oil together in a small bowl until mostly combined. With clean hands, rub the mixture over the surface of the chicken and under the breast skin.

Place the chicken on the wire rack breast side up. Tie the legs together with kitchen twine, and tuck the wing tips beneath the body of the chicken.

Cut the baguette into 1/2-inch cubes.

Finely dice the onion and celery. Mince the garlic.

Set a large skillet over medium heat and melt the butter, then add the onion and celery. Sauté, stirring occasionally, until the vegetables are soft and translucent, 5-7 minutes.

Add the garlic and dried herbs to the skillet and sauté for 30 seconds longer.

Add the bread cubes to the skillet. Stir with a rubber spatula to coat. Season with salt and black pepper.

Remove the skillet from the heat and transfer the contents to a large mixing bowl.

Drizzle chicken broth over the bread cubes. Stir until the bread is evenly moistened.

Spoon the stuffing into the chicken, taking care not to pack it too tightly. There may be some stuffing left unused.

Roast the chicken on middle rack of oven until the thickest part of the breast reaches an internal temperature of 160°F, 60-80 minutes.

Check to see that chicken is done. Remove from oven or add time as needed.

Allow chicken to rest for 10 minutes before serving. Leftovers may be refrigerated for 3-4 days or frozen for up to 2 months.