How to Make It
In a medium saucepan of boiling water, cook the udon until tender, 5 minutes. Drain and toss with 1 teaspoon of the canola oil.
Meanwhile, heat a wok until very hot. Add 2 tablespoons of the canola oil and when it starts smoking, add the clams. Cover and cook for 2 minutes. Add the ginger, garlic, parsley and black bean sauce and stir-fry for 2 minutes. Add the sake, cover and cook until the clams open, about 5 minutes longer. Pour the clams and their juices into a large bowl.
Return the wok to high heat and add the remaining 2 tablespoons of canola oil. Add the watercress and stir-fry until crisp-tender, about 2 minutes. Add the udon, oyster sauce and butter and stir-fry until the udon are evenly coated. Return the clams and any accumulated juices to the wok and stir-fry just until combined. Transfer to the bowl, garnish with the scallion and drizzle with chile oil. Serve immediately.