Thinly slice the beef against the grain at a 45 degree angle. Each slice should be a little thicker than ⅛ inch but thinner than ¼ inch in thickness.
Quick marinade
In a bowl, add the ingredients from beef to starch. Gently mix them well and set aside in the fridge for 10-15 minutes or up to 24 hours.
Preheat the pan
Preheat a 12 inch large saute pan over medium heat. Carefully place your hand 2.5-3 inches away from the pan surface to test the temperature. When it feels too warm to place your hand nearby, the skillet is ready. If your panis overheated (i.e. smoking), simply set it aside for a few minutes to cool down a bit.
Sear the beef
Add the oil. Add the beef and quickly spread them out into a single layer. You should hear sizzling sound. This means your pan temperature is correct. Pan sear the beef over medium-high heat without disturbing for about 2 minutes or until the beef is in golden brown color. Some beef slices might overlap with one another and that’s totally okay.
Use a spatula with a firm tip to flip the beef and sear the flip side for 30 seconds extra. Please don’t over cook the beef or they will turn watery.
Turn off heat. Transfer the beef and the pan juice onto a serving plate. Garnish with scallions and sesame seeds, if using.
Video
Notes
If you use soy sauce to marinate the beef, reduce the quantity to 1/2 tbsp for 1lb of beef and you do not need fish sauce. Season the beef with a touch of sugar if needed to balance the salty flavor.
Coconut aminos naturally tastes sweeter and less salty than regular soy sauce.