Super tender beef stir-fry

Name: Super tender beef stir-fry
Prep time: 10 min
Cook time: 20 min
Total time: 30 min
Cuisine: Chinese, Asian
Ingredients: 2 x 250g (9 oz) striploin steaks (sirloin, rib-eye, scotch fillet or rump steaks are also fine to use); 2 tbsp vegetable oil; 3 garlic cloves, roughly chopped; 1 onion, sliced; 2 capsicums (bell peppers), deseeded and cut into bite-sized pieces; 2 spring onions (scallions), finely chopped; 1 tbsp soy sauce; 1 tbsp Chinese Shaoxing wine*; ½ tsp bicarbonate soda (baking soda); 3 tsp cornflour (cornstarch); 3 tbsp oyster sauce; 3 tbsp Chinese Shaoxing wine*; 2 tbsp soy sauce; ½ tsp dark soy sauce; 2 tsp sugar; 1½ tsp ground black pepper; 2 tsp white vinegar