Wipe mushrooms clean and chop, if large. Finely slice leeks or onions. Put a few teaspoons water in a non-stick pan and fry leeks (onions), garlic, ginger and curry leaves until soft (add water as necessary). Add curry powder, salt and mushrooms, stir until mushrooms release liquid, then cover and cook on low heat 8-10 minutes. Sprinkle with garam masala or nutmeg, add apple juice and cook uncovered, stirring until heated through. Remove from heat and stir in lemon juice. Serve with rice.