Step 1

In a large pot, bring 3 quarts water to a boil. Add the noodles and cook, stirring occasionally, until just shy of al dente. Reserve ¼ cup of the cooking water, then drain the noodles in a colander. Rinse under cold water until cool to the touch, then drain again; set aside.

Step 2

In the same pot over medium-high, melt 2 tablespoons butter. Add the mushrooms and cook, stirring occasionally, until beginning to brown, about 3 minutes. Reduce to medium and add the garlic; cook, stirring, until fragrant, about 30 seconds. Add the noodles, followed by the soy sauce; cook over medium-high, stirring and tossing, until heated, about 1 minute.

Step 3

Add the reserved cooking water and the remaining 2 tablespoons butter; cook, tossing, until the noodles are slick, glossy and tender, about 2 minutes. Off heat, taste and season with additional soy sauce. Serve sprinkled with sesame seeds