The buns should be quite dry. Leave them out overnight or dry them in a very slow oven at about 250 degrees. Crumble the buns into a large bowl, there should be about twelve cups. Melt the butter in a large skillet and add the onions and the celery. Saute slowly until tender, about fifteen minutes. Add to the crumbled buns, along with the salt, pepper and sage. Add the bouillon cubes to the boiling water and stir until dissolved. Beat the eggs lightly in a small bowl and stir into the dressing. Add enough of the chicken broth to make a moist mixture. Stuff the turkey cavity lightly with the dressing. Spoon any extra dressing into a buttered casserole. Spoon a little extra chicken broth over the top and bake uncovered or covered with the turkey during the last half hour of roasting.