Crispy Chilli Beef

Ingredients:
360 g thin-cut sirloin steaks, cut into thin strips
1 small egg
4 tbsp cornflour (cornstarch)
¼ tsp salt
¼ tsp black pepper
⅛ tsp white pepper
4 ½ tbsp sunflower oil, divided
1 medium onion, sliced into thin strips
1 red chilli, finely sliced
1 tsp minced ginger
3 garlic cloves, minced
2 tbsp rice vinegar
3 tbsp dark soy sauce
2 tbsp tomato puree (paste)
6 tbsp caster sugar
2 tbsp tomato ketchup
2 tbsp sweet chilli sauce
Instructions: