Rinse turkey and pat dry.
Cut across the grain into 3/8-inch-thick slices.
In a large baking dish, combine sherry, stock base, and rosemary leaves.
Stir to dissolve stock base.
Add turkey and turn to coat.
Cover and refrigerate until next day, turning occasionally.
Prepare Cashew Butter; keep warm.
Lift turkey from marinade and drain briefly (discard marinade).
Place turkey on a lightly greased grill 4 to 6 inches above a solid bed of medium coals.
Cook, turning and basting occasionally with plain melted butter, until meat is no longer pink in center; cut to test (about 8 minutes).
Transfer turkey to a platter and garnish with rosemary sprigs and lemon wedges.
Pass Cashew Butter to spoon over individual portions