Chinese Cabbage with Vinegar

Name: Chinese Cabbage with Vinegar (Cu Liu Bai Cai 醋溜白菜)
Cuisine: Chinese
Ingredients: 1 tsp potato flour mixed with 1 tbsp water (optional); 2 tbsp cooking oil; 2 tsp Chinkiang vinegar; ¼ tsp caster sugar; 300 g Chinese leaf cabbage; Salt