1. Make sauce Blend cornflour and soy sauce together until smooth. Combine sugar, tomato sauce, vinegar, pineapple, pineapple juice and soy mixture.
2. Heat a wok over medium-high heat. Add peanut oil. Swirl to coat. Add onion, celery and carrot. Stir-fry for 3 minutes or until softened slightly. Add sauce mixture to wok. Cook, stirring, until mixture comes to the boil. Remove from heat.
3. Pour egg into a bowl. Add pork. Toss to coat. Pour oil into a large heavy-based saucepan until it is one-third full. Heat over medium-high heat until a piece of bread dropped in browns in 15 seconds.
4. Coat one-third of the pork in cornflour, shaking off excess. Lower into oil. Cook for 1 to 2 minutes or until golden and cooked through. Drain on paper towels. Repeat twice with remaining pork.
5. Return sauce to stovetop over medium heat. Cook for 2 minutes or until hot. Add pork and toss to coat. Cook for 2 to 3 minutes or until heated through. Serve with steamed rice and Asian greens.