Pull off husks from tomatillos and rinse tomatillos well. Place in a 10- by 15-inch baking pan and bake in a 400° oven until slightly browned and soft when pressed, 25 to 30 minutes. Meanwhile, rinse, stem, seed, and chop the green jalapeño chile; rinse cilantro and parsley. Transfer tomatillos to a blender or food processor and add chile, cilantro, parsley, and olive oil. Pulse until mixture is coarsely chopped and slightly chunky.