Spring rolls with crisp oyster mushrooms and dipping sauce

Name: Spring rolls with crisp oyster mushrooms and dipping sauce
Ingredients: 1 tbsp coriander stems, chopped; 1 tbsp vegetable oil; 100g/3½oz oyster mushrooms, torn into strips; 100ml/3½fl oz Chinese plum sauce; 12 spring onions, finely chopped; 2 apples, peeled and cut into matchsticks; 2 carrots, julienned; 2 cloves garlic, sliced; 20 spring roll wrappers; 50g/2oz five spice powder; 50g/2oz plain flour; 50ml/2fl oz thick soy sauce; 5cm/2in piece of ginger, cut into matchsticks; salt to season