Place potatoes into a large pot and cover with salted water. Bring to a boil over high heat, then reduce heat to medium-low, cover, and simmer until tender, about 20 minutes. Drain and allow to steam dry for a minute or two, then mash.

Melt the butter in a skillet over medium heat; cook the celery and onion in the butter until the onion has turned translucent, 5 to 7 minutes. Fold into the mashed potatoes along with the savory, and allow to cool until just warm.

Place the cooled mashed potatoes into a large bowl, and stir in the beaten egg. Gently fold in cubed bread, then season to taste with salt and pepper. Refrigerate until ready to use.

Use as a stuffing for turkey, or bake in buttered loaf pans at 350 degrees F (175 degrees C) for 30 to 40 minutes.