1. Wash the apple, cucumber, celery and mint leaves thoroughly.
2. Cut the apple, cucumber and celery into small pieces.
3. Peel the lemon and remove any visible seeds.
4. Add the apple, cucumber, celery, lemon, mint leaves and cold water to a blender.
5. Blend until smooth and well combined.
6. Add ice cubes and blend again for a chilled texture.
7. Strain the juice if a smoother consistency is preferred.
8. Pour into chilled glasses.
9. Garnish with fresh mint and a lemon slice.
10. Serve immediately for the best flavour and freshness.