Step 1

Fill a large pot two-thirds full with water. Bring to a boil over high heat. When water starts to steam, toss in a small handful of salt.

Step 2

While you wait for the water, do some of your prep: Cut 1 chile in half lengthwise. Using your hands, pull out and remove stem and white ribs; discard. Tap out and discard any seeds, then finely chop chile. (Make sure to wash your hands with plenty of soap and hot water after handling chiles, or at least don’t rub your eyes!)

Step 3

Cut 4 cucumbers in half lengthwise, then slice crosswise into ¼"-thick half-moons.

Step 4

Thinly slice 4 scallions.

Step 5

Cut 2 limes in half. Using a citrus reamer (or fork if you don’t have a reamer), juice limes into a small liquid measuring cup until you have ¼ cup; discard seeds. Cut remaining 1 lime into wedges; set aside for serving.

Step 6

Whisk ½ cup miso, 4 tsp. sesame oil, 4 tsp. brown sugar, and ¼ cup lime juice in a large bowl until smooth.→ Here are 5 more ways to use up a tub of miso.

Step 7

Finely grate 1 garlic clove into bowl and whisk to combine.

Step 8

Whisking constantly, slowly stream in ⅓ cup grapeseed oil until dressing is smooth and thick. Whisk in water 1 Tbsp. at a time until dressing is the consistency of heavy cream (it’ll likely take about 2 Tbsp.).

Step 9

When water is boiling vigorously, add 1 lb. pasta to pot and stir with tongs to prevent sticking. Cook according to package instructions.

Step 10

Drain noodles in a colander and rinse with cold water to stop cooking and remove any starch. Drain thoroughly, shaking off excess water, then add to bowl with sauce.

Step 11

Toss noodles to coat in sauce, then add chile, cucumbers, and scallions. Season with more salt to taste and toss again to distribute.

Step 12

Divide noodles among plates. Top with toasted sesame seeds and serve with reserved lime wedges alongside.

Step 13

Do Ahead: Noodles can be made several hours ahead. They tend to soak up a lot of the sauce as they sit, so if you want to make the day before, hold back half of sauce, cover, and chill. Toss with reserved sauce before serving.