Clean, wash and slice the celery and blanch it in bubbling salt water for 2 minutes, rinse in cold water and drain on a sieve. Wash tomatoes, dab dry and cut into slices.
Mix cream with sugar and lemon juice. Wash the lemon balm, chop finely and add to the dressing. Season with salt and pepper. Drain the shrimps in a sieve. Mix the shrimps, celery and tomatoes in a bowl with the dressing.
Arrange the cocktail in glasses and garnish with celery leaves.