Look for sturdy green pods with a velvety fuzz. Avoid any with slimy brown spots or overly large beans.
Stir together mint or cilantro, olive oil, salt, and pepper. Grill fava bean pods directly on grates over high heat, turning, until charred, 10 to 12 minutes. Let cool slightly. Sprinkle with mint or cilantro, lemon juice, and salt. Serve with herb sauce and lemon wedges.