Preheat your oven to 375°F (190°C). Sauté the onion and celery in a skillet over medium heat for 5-7 minutes until soft and fragrant.
In a large mixing bowl, combine the cubed stale bread, sautéed onion, celery, parsley, sage, thyme, salt, and pepper. Mix well.
Pour the vegetable broth over the mixture and stir gently until the bread is moistened. Add the beaten eggs and cheese (if using) and mix until combined.
Shape the mixture into balls about 1.5 inches in diameter and place them on a baking sheet lined with parchment paper.
Bake in the preheated oven for 25-30 minutes until golden brown and crispy on the outside.
Let the stuffing balls cool slightly before serving.