I've used many chap chae recipes over the years, so my version has elements of all of them. As with pretty much any stir-fry, most of the work is in the prep for this dish. You could do the rinsing, chopping, soaking and marinating hours ahead of time, leaving only 15 minutes of stove time for later. Be sure you keep the wok very, very hot and well oiled as you stir-fry, so nothing sticks.

1/2 to 3/4 pound beef sirloin (about 1-inch thick)

6 or 7 dried black mushrooms (dried shiitake mushrooms, available at Asian groceries), or fresh shiitakes

1 pound Korean sweet potato noodles

1 bunch spinach or 1/2 pound baby spinach leaves

1 tablespoon hulled white sesame seeds

1/2 cup soy sauce (or gluten-free tamari)

Place the beef in the freezer while you're working on the other ingredients. That will make it easier to slice. Soak the dried mushrooms in boiling water, weighting them with a plate or the bottom of a bowl so they stay beneath the surface of the water. Soak the sweet potato noodles in plentiful hot tap water (if you're working several hours ahead, soak the noodles just before stir-frying. They take about 10 minutes to soften up).

Wash the spinach in several changes of cold water and trim the stems; you can leave the stems if you're using baby spinach.

Toast the sesame seeds briefly in a small, heavy skillet over medium heat. They're done when they show just a bit of golden browning.

Halve the onion and slice thinly. Peel and julienne the carrots (easiest if you halve them lengthwise first, then slice into 1/8-inch thick slices, then cut into matchsticks). Halve the scallions lengthwise and cut into 1-inch lengths.

Squeeze out the dried mushrooms, reserving the soaking liquid. Cut off and discard the stems and slice the caps 1/8-inch thick.

Take out the partially frozen beef. Holding your knife parallel to the cutting board, slice the beef into two 1/2-inch-thick halves. Then slice against the grain into strips about 1/8-inch thick and about 2 inches long. Place the meat in a nonreactive bowl. Drain the noodles.

In a small bowl, mix together the garlic, soy sauce or tamari, brown sugar and sesame oil for the sauce. Spoon a few tablespoons of the sauce onto the sliced beef and toss thoroughly. Add about 1/4 cup of the mushroom soaking liquid to the sauce (you can discard the rest of the mushroom liquid).

Place a capacious wok over high heat. When it begins to smoke, add half the peanut oil (1 1/2 tablespoons) and the onion, carrots, scallions and mushrooms. Stir-fry for about 2 minutes, until just becoming tender. Push to one side of the wok.

Add a little bit more of the peanut oil, swirl it about and spread out the marinated meat in a single layer at the bottom of the wok. Let it sit briefly to develop some browning, then mix in with the vegetables and push to one side of the wok.

If the wok is dry, swirl in the remaining peanut oil. As soon as it is smoking-hot, add the drained noodles. Pull the meat and vegetables back atop the noodles, mix together, and add the sauce. Stir-fry, mixing well. Finally, toss in the spinach and sesame seeds and serve.