1. Bring 5 cups water to a boil in a large saucepan. Add tomatillos, chiles, onion, and garlic; cook 5 minutes or until tender. Drain well; place tomatillo mixture in a blender. Add 1/2 cup cilantro; process until smooth, stopping to scrape down sides.
2. Heat oil in a deep skillet or saucepan over medium-high. Carefully add tomatillo sauce (it will splatter); bring to a simmer. Reduce heat to medium. Add purslane; cook 2 minutes or until just wilted, stirring constantly. Stir in salt and remaining 1/2 cup cilantro.