Wash and dry the vegetables. In a wide bowl, pick the lettuce leaves with your hands. It should definitely be crunchy varieties: cheese, frisee, iceberg or something in this style.
If possible, remove the hard threads from the celery stalks and cut the stalks themselves into thin slices. Add to the bowl.
Cut the cucumber lengthwise and then crosswise into slices. Send it there.
Have fennel cut off the upper rough stems, greens to leave for salad. Remove the two upper rough scales, they can then be used for cooking vegetable broth. Cut the onion in half and then crosswise with thin petals. Add to the bowl.
Peel the Apple and remove the seed pods, cut it into thin slices or slices as you like, and add it to the rest of the ingredients.
Finely chop the greens and add them to the salad. Add salt and pepper, preferably freshly ground pepper, to taste. Then mix everything carefully and easily with your hands. In a small jar, pour the oil and juice, tightly screw the lid and shake vigorously for 10 seconds. You will get such a wonderful sauce-emulsion.
Lightly sprinkle the resulting emulsion on the salad and mix it very easily and gently.