Place the tomatillos on a hot skillet and roast for a couple of minutes or until blackened on all sides. Saute the onion and garlic in the oil until soft. Place the tomatillos, onion mixture, lime juice, and black pepper in a blender and puree until smooth. Stir in the cilantro. Marinate the shrimp in the mixture for an hour. Remove and thread on skewers along with the chile strips. Grill until just done (a few minutes on each side) and serve with the sauce on the side.