Wash the celery and cut into pieces approx. 1-2 cm, blanch in salted water for approx. 4-5 minutes, then drain in a sieve.
Heat the butter in a non-stick pan, add the celery, add salt and sugar and finish cooking over medium heat. Caramelize until the liquid is pretty much gone and the celery pieces are a little browned. Turn around from time to time. Grind some fresh pepper over it.