Step 1

Place half of spring onions in a large heatproof bowl and set a fine-mesh sieve on top; set aside. Combine remaining spring onions with ginger, garlic, and oil in a small saucepan. Set over medium-high and cook, stirring occasionally, until garlic is golden and scallions are beginning to crisp and turn golden brown, 8–10 minutes.

Step 2

Pour mixture through reserved sieve onto spring onions. Turn out garlic crisp in sieve onto paper towels to drain. Stir spring onions in bowl until just softened, about 1 minute. Stir in chile, herbs, soy sauce, vinegar, sesame seeds, pepper, salt, and sugar. Let dressing sit 10 minutes.

Step 3

Meanwhile, cook noodles according to package directions. Drain and rinse under warm water to get rid of any excess starch.

Step 4

Transfer noodles to bowl with dressing and add butter and half of garlic crisp; toss to coat noodles. Divide among bowls; top with remaining garlic crisp.