Season the birds with salt and pepper. Stuff each one with sage leaves and a prune. Skewer on the spit and place in front of hot part of coals with a drip pan. Cook until just cooked through (depending on your fire, about 45 minutes to 11/2 hours).
Meanwhile, place remaining sage and prunes into a 1 quart sauce pan with stock, vin santo and tomato conserve. Simmer 30 minutes. Remove birds from spit, cut in half and serve with prunes and roasted potatoes.
Recipe Courtesy of Mario Batali