Preheat Oven To 400F. Rinse quails and pat them dry with paper towels. Lay a round of pancetta over breast and thighs of each bird and tie securely with string. Melt butter in an oven-proof casserole just large enough to hold quails. Add sage leaves and quails. Brown them over medium heat 3-to-4 minutes on each side. Sprinkle with salt and pepper, and pour on the wine. Set casserole in oven and bake 20-to-25 minutes, until tender, turning quails once after 10 minutes. Remove strings and serve in a heated dish.