Dry bread cubes:

Set oven to 250°F (120°C). Arrange bread cubes on two rimmed baking sheets. Bake for 15 minutes, stirring and rotating pans halfway, until dried but not browned. As an alternative, allow bread cubes to sit loosely covered on counter for 24 hours to dry.

Preheat oven and grease dish:

Raise oven temperature to 350°F (175°C). Grease a 13x9-inch baking dish lightly.

Sauté onion and celery:

In a large Dutch oven or skillet over medium-high heat, melt butter. Add onion and celery; cook, stirring occasionally, until softened, about 6 minutes.

Add herbs and seasonings:

Stir in garlic, parsley, sage, rosemary, thyme, salt, and pepper; cook for 1 minute, then remove from heat.

Whisk broth and egg:

In a liquid measuring cup or bowl, whisk together broth and egg until combined.

Combine bread and vegetables:

If the bread cubes fit in the pot with vegetables, add them and stir to combine. Otherwise, transfer bread cubes to a large bowl and add the vegetable mixture; stir.

Add broth mixture:

Pour the broth-egg mixture over the bread cubes and stir. The bread should be moist but not soggy. If it seems dry, add more broth until lightly moistened. For a moister stuffing, use more than the 1½ cups listed.

Bake covered then uncovered:

Transfer the mixture to the prepared dish and spread evenly. Cover with foil and bake for 30 minutes. Remove foil and bake an additional 15-25 minutes, until the top is browned and the center reaches at least 160°F (70°C) on an instant-read thermometer.