If using flank steak, follow same instructions as steak strips.
If using diced chicken breast, follow same instruction as steak strips in Steps 2 and 3, stirring occasionally until chicken reaches a minimum internal temperature, 5-7 minutes per side.
If using tofu, line a plate with a paper towel. Cut tofu into 1" dice and place on towel-lined plate. Top with paper towels, then press gently but firmly to remove excess moisture. Follow same instructions as steak strips in Step 3, stirring occasionally until lightly browned, 6-8 minutes.