Preparations

Wash, cut, and blanch the spinach. If you are working in advance, refrigerate the spinach sealed airtight. Bring to room temperature before using.

Leave the rubber bands or strings binding the noodles in place, then put the noodles in hot tap water to cover until rubber-band firm, 1–3 minutes. Drain, cut into 4–5-inch lengths, then cut and discard the rubber bands or strings. Rinse the noodles in cool water and drain well, shaking to remove excess water. If you are working in advance, cover the noodles with cool water and drain thoroughly before using.

Cooking the noodles and stir-frying the spinach

Have all the ingredients and a heatproof colander or large strainer within easy reach of your stovetop. Put a shallow serving bowl of contrasting color in a low oven to warm. Fluff the spinach to loosen the mass.

Combine the noodles and stock in a small saucepan. Bring to a simmer over moderate heat and cook very gently until the noodles turn soft and silky, 2–5 minutes. Swish the noodles once or twice as they simmer and keep an eye on them lest they turn mushy. (In the course of simmering, the noodles will absorb most if not all of the stock.) Once silky, drain the noodles in the colander to remove excess stock, then proceed immediately to stir-fry the spinach.

Heat a wok or large, heavy skillet over high heat until hot enough to evaporate a bead of water on contact. Add the oil, swirl to glaze the pan, then reduce the heat to medium-high. When the oil is hot enough to sizzle a bit of spinach on contact, add the spinach and toss briskly to separate the leaves and gloss them with oil, about 15 seconds. Sprinkle with salt and sugar, then toss rapidly to combine and heat through, 30–40 seconds. Work quickly over crackling heat, lest the spinach get watery. Add the noodles and blend with rapid scooping motions until hot to the touch. Sprinkle in the sesame oil, stir 2 or 3 times to combine, then remove to the heated platter. Pause briefly to arrange the vegetable prettily, then serve.

Leftovers keep 2–3 days, sealed and refrigerated, and are tasty at room temperature.