Peel and halve the onion and cut into pieces. Clean and wash the cucumbers and also cut them into pieces. Wash and clean the celery and cut it into large pieces. Wash parsley, shake dry and chop coarsely.
Puree cucumbers, onion, celery, wasabi, sour cream, water and oil very finely in a high performance blender. Season to taste with salt, pepper and lemon juice. Chill the soup for about 1 hour.
Leave the bacon in a pan without fat until crispy. Pour cucumber soup into glasses (à approx. 350 ml), arrange with bacon.