Wash the celery and cut into pieces approximately 1-2 cm. Blanch in boiling salted water for 4-5 minutes, then drain in a sieve.
Heat the butter in a non-stick pan over medium heat. Add the celery, a bit of salt, and the sugar. Stir every 1-2 minutes until the liquid has evaporated and the celery pieces are golden brown. Grind some fresh black pepper over the top.