Slice the steak in ¼-inch slices. Lay the slices flat, cover with plastic wrap and use a meat pounder to flatten the meat.
Put the meat in a ziploc bag and add the cornstarch. Massage the steak and cornstarch together to make sure each piece is fully coated.
Pour the canola oil into a large frying pan, and heat on medium high heat.
Add the steak to the pan in a single layer and cook for 30 seconds per side (1 minute total). Cook the steak in batches rather than over-crowding the pan.
Remove the steak from the pan as it finishes cooking, set it aside on a plate, then sprinkle with salt.
Next, add the ginger, garlic, and chili oil or red pepper flakes (if desired for more spice) to the pan and sauté for 10-15 seconds.
Stir in tamari (or soy sauce), water and brown sugar and bring the mixture to a boil.
Fold the steak back in and let the sauce thicken for 20-30 seconds.
Turn off the heat, add the green onions, and stir to combine.
Serve over white rice, rice noodles or in lettuce wraps.