Bring a medium pot of water to a boil. Cook beans in water until bright green and tender, about 5 minutes. Drain.
Heat oil in a wok or large frying pan over high heat. Add beans and cook, stirring frequently, until starting to brown, about 4 minutes. Mix XO sauce and hoisin in a small bowl. Add sauce to beans, stirring to coat, and cook until sauce is fragrant and coats beans, about 3 minutes.
*Find long beans and XO sauce, a dried seafood-based condiment, at Asian grocery stores.
Make ahead: Up to 1 day, chilled; microwave to rewarm.
Note: Nutritional analysis is per serving.