1. or the beef: Heat a wok over high heat and fill halfway up with peanut oil. Heat the oil to 350 degrees F, or until a cube of bread turns golden brown in 15 seconds and floats to the surface.
2. Place the beef strips in a large bowl and add 2 tablespoons cornstarch. Toss until the beef has absorbed the cornstarch. Add the remaining 1 tablespoon cornstarch right before frying and toss to coat.
3. Fry the beef in two to three batches until golden, four to five minutes. Drain on paper towels and season with sea salt.
4. For the sauce: Set another wok or saute pan over high heat and add the soy sauce, chilli sauce and orange juice. Bring to a simmer and cook until it becomes thickened and coats the back of a spoon, one to two minutes. Toss the beef in the sauce to coat thoroughly.
5. Serve over a bed of the shredded lettuce and sliced cucumber that has been sprinkled with rice vinegar. Then garnish with the scallions and orange zest.