In a large bowl, whisk together sesame paste (¼ cups), peanut butter, soy sauce (3 tbsp), sugar (2 tbsp), vinegar, and chili oil (2 tbsp). The mixture will seize up and look like cement. This is normal—it's a sludge at this stage.

Don't panic when it looks too thick—that's expected • Thick, tan-brown paste that looks too thick to use • Strong sesame and peanut aroma

Add hot water (¼ cups), 1 tablespoon at a time, whisking constantly. Keep adding and whisking until the sauce transforms into a pourable cream. It should ribbon off the whisk smoothly.

Add water gradually. Too much at once and it won't emulsify. • Creamy tan sauce that ribbons off whisk

Bring a large pot of salted water to a boil. Cook noodles according to package directions until al dente. Drain.

Salt the water well—noodles absorb flavor here • Tender noodles with slight bite

Rinse noodles under cold running water until completely cool to the touch. Shake dry thoroughly in the colander. If you don't dry them, the sauce will slide off.

Unlike Italian pasta, Asian cold noodles must be rinsed to remove starch • Cool noodles that don't stick together • Noodles feel cool and dry, not slippery

Add noodles to the bowl with the sauce. Toss vigorously with tongs or chopsticks until every strand is coated. Drizzle with sesame oil (1 tbsp) and toss again.

Get in there with your hands if needed—every strand should be coated • Glossy tan noodles with no dry spots

Top with scallions (3 whole) and cucumber (1 medium). Serve at room temperature or cold.

These improve after sitting 30 mins—flavors meld • Tan noodles topped with green scallions and pale cucumber