To prepare the greens: Soak the greens in a big bowl of water and wash well to remove any dirt from the leaves. Depending on the type of greens you’re using, if needed, cut them into smaller pieces and trim any dry, tough stem ends.
In a wok or frying pan over high heat, warm the oil until almost smoking. Add the chile pepper, garlic, and ginger and stir-fry quickly for 30 seconds. Add the greens and stir-fry for about 1 minute, until cooked but still green.
Add the fish sauce and soy sauce and stir to ensure the ingredients are thoroughly seasoned. Stir in the sesame oil at the very end, remove the wok from the heat, transfer the vegetables to a platter, and serve immediately.
