To plump the raisins, combine them with the apple cider in a small saucepan and bring to a boil over medium heat. Immediately remove from the heat and set aside.
In a large, nonreactive saucepan or Dutch oven, melt the butter over medium heat. Add the onion, celery, and pine nuts. Cook, stirring occasionally, without coloring, 6 to 8 minutes.
Add the mortadella, olives, apples, and sage and cook 5 more minutes.
Strain the raisins, reserving the cider, and add the raisins to the saucepan. Stir in the bread cubes, season with the salt and pepper, and add reserved cider. Bring to a boil, lower the heat and simmer, covered for 15 minutes. Stir thoroughly, cover, and continue cooking for an additional 15 minutes. The stuffing will be very moist. Serve hot. The stuffing can be kept hot and held for up to 1 hour in a bain-marie.
Recipe courtesy of Michael Romano