Place a grill pan or skillet over medium high heat, when hot add tomatillos and chiles, allow them to cook about 5 minutes per side until nicely charred. Transfer charred tomatillos and chiles to a food processor fit with a steel blade or a blender along with half of the cilantro, half of the green onions, garlic, cumin, salt, pepper and water and pulse until well combined. Pour into a bowl and stir in remaining cilantro and onions, taste for salt and adjust to taste.