Serves 4 to 6
In a small bowl, combine vegetable stock, soy sauce, sake, oyster sauce, ponzu, miso, and palm sugar and whisk well to combine. Set aside.
Heat 1/4 cup oil in a wok over high heat. When hot, add oyster mushrooms and a pinch of salt, and cook until mushrooms begin to brown and wilt, about 2 minutes. Add shiitake mushrooms and another pinch of salt and continue to cook until mushrooms are nicely browned, 2 to 3 minutes longer.
Arrange watercress on a large serving platter. Add the remaining tablespoon oil, bell pepper, and red onion and cook until vegetables just begin to soften, about 2 minutes. Add garlic and ginger and cook until fragrant, about 30 seconds. Add noodles and reserved sauce and toss to combine. Cook until heated through, 1 to 2 minutes. Remove from heat and transfer to platter over watercress. Garnish with carrots, reserved green onion tops, cilantro, and watercress. Drizzle with hot sesame oil and toss quickly to combine. Serve immediately.