This side dish has popping flavors and is so easy to make! If you haven’t tried maitake mushrooms yet (also called Hen of the Woods), they have a deep, rich flavor similar but more mild than a porcine or truffle mushroom. But if you can't get your hands on maitake mushrooms, you can always use shiitake for that strong flavor profile.
In a large skillet, heat oil until hot but not smoking (medium high works well). Add the onion and sauté until just starting to soften, then add the garlic, ginger and Thai chile pepper, if using. Stir for one minute, then add the long bean and continue to sauté for 2 to 3 more minutes. Then add the maitake mushroom and season with garlic salt and black pepper. Keep gently stirring (try not to break up the mushroom pieces) and when the mushroom starts to slightly wilt, turn off the heat. Drizzle with sesame oil, sprinkle with black sesame seeds and top with crispy shallots.