In a dry heavy skillet, toast the garlic and serranos over medium heat, until slightly charred. Remove. Add the pumpkin seeds to the skillet and toast until browned. Transfer the garlic, serranos, and seeds to a blender, along with the poblanos, herbs, oil, and lime juice. Blend, adding water as necessary, until a smooth thick dipping paste, like pesto, is formed. Season with salt and pepper and blend to combine.