Step 1

Cook scallion whites, vegetable oil, red pepper flakes, sesame seeds, and pepper in a small saucepan over low heat, stirring occasionally, until oil is sizzling and scallions are golden brown, 12–15 minutes; let chili oil cool in saucepan.

Step 2

Meanwhile, cook noodles in a large pot of salted boiling water until al dente; drain. Rinse under cold water and drain well.

Step 3

Whisk tahini, vinegar, soy sauce, sesame oil, sugar, and 2–3 tablespoons chili oil (depending on desired heat) in a large bowl; season with salt. Add noodles and toss to coat. Top with scallion greens and drizzle with more chili oil.