Tenderise beef - toss with baking soda, leave 20 min, rinse, season with soy sauce. Stir fry - Sauté onion first, then beef, then garlic, then stems. Add leafy greens, prepared noodles, and sauce. Toss well then serve.

Tenderise - Sprinkle the beef with baking soda in a small bowl. Toss with your fingertips to coat, separating the beef slices. Leave for 20 minutes to tenderise.

Rinse, dry, season - Rinse in a colander, shake and pat off excess water with a paper towel (no need to be thorough). Place in a bowl and toss with the soy sauce. Set aside. (It doesn't need to marinating time).

Sauce - Mix ingredients in a small bowl.

Soak and rinse noodles - Prepare the noodles according to packet directions (usually soaking in boiling water for 5 - 10 minutes). Drain, then rinse under tap water to remove excess starch so it doesn't go gluey when cooked.

Cook onion, beef then garlic - Heat the oil over high heat in a large wok or large deep fry pan / skillet (~30cm/12"). Add the onion for 30 seconds. Add beef and cook until the red is almost gone (~1 minute), then add the garlic and cook for 30 seconds.

Stems then everything else - Add the stem part of the Asian greens, toss for 1 minute. Add the leafy part, noodles then sauce (in that order). Toss for 1 1/2 to 2 minutes until the sauce has stained all the noodles and there is no sauce left in the base of the pan. Serve immediately!