Butterfly turkey by cutting each tenderloin in half horizontally, cutting almost to the opposite side. Spread open. Sprinkle both sides with salt and pepper.
For stuffing, in a small saucepan bring broth to boiling. Stir in couscous, dried cherries, and shallot. Remove from heat. Cover and let stand for 5 minutes. Fluff with a fork. Stir in pistachios and snipped sage. Spread in a shallow baking pan to cool quickly.
Spread filling over turkey; fold turkey over filling to enclose. Top with pancetta and sage leaves. Tie at 2-inch intervals with 100% cotton kitchen string, tucking leaves under string as necessary.
Wrap each tenderloin in plastic wrap. Place in a freezer bag or container; seal and freeze for up to 1 month.
To serve, thaw in the refrigerator overnight. Preheat oven to 375°F. Unwrap tenderloins and place on a greased baking sheet. Bake for 40 to 45 minutes or until turkey is done (165°F). Remove from oven. Cover loosely with foil and let stand for 5 to 10 minutes. Remove string; slice turkey.