Slice steak length-wise into thin strips, about 1/4 inch wide. Using my slicer this was setting 4. Freezing the steaks for about a half hour will make them easier to slice.
Mix the water and baking soda in a medium bowl. Add the beef strips and toss to coat the beef. Set aside for 5 minutes.
Place the shallots (quartered), sugar, soy sauce, garlic, sesame oil and black pepper into a blender. Blend until smooth. Add to the bowl of beef. Toss to coat.
Heat the largest pan you have over high medium high heat. Divide the beef, scallion tops, and vegetable oil into batches that your pan can accommodate. A 12" pan will require 2 batches. Add the oil for one batch to the pan and heat till starting to smoke. Add, in a single layer, one batch of the beef. Allow to cook without turning for about 2 minutes or until well browned, then start stirring the beef until browned on both sides. Add the scallions for this batch and stir for about 15 seconds. Set aside and prepare the next batch.