Step 1

Bring a large pot of lightly salted water to boil, add the noodles and cook according to package directions; drain.

Step 2

Meanwhile, fill a medium pot with about 2 inches of water and bring it to a boil. Place a steamer basket over the top so that it does not touch the water. Arrange the bok choy in the basket – it's okay if the vegetables overlap – then reduce the heat to low, cover with a tightfitting lid and steam until tender, 5 to 7 minutes. Uncover and turn off the heat.

Step 3

While the bok choy steams, in a large heat-proof bowl, whisk together the sesame oil, chili oil, sesame seeds and soy sauce, garlic and red pepper flakes until combined.

Step 4

In a small saucepan over medium heat or in a microwave-safe bowl, heat the vegetable oil until shimmering, about 2 minutes on the stove, or about 45 seconds on HIGH in the microwave. Pour the hot oil over the chili oil mixture and whisk until fully combined. Add the noodles and toss until each strand is well coated.

Step 5

Divide the noodles and bok choy among warm, shallow bowls. Sprinkle with the black pepper, if using, the scallions and chile, if using, and serve.