Email Albert Raurich - Chef de Cuisine - NOW. His email address is email@example.com. He'll start reading every single request starting tomorrow - December 1st. Also - if I were you - I'd fill out the CV form on the website too - click here. They're looking to fill 20 to 22 places for the full six month season - maybe another 18 to 20 for one or three months. Last year Albert had 800 requests. This year - by the end of the September - he had 1600 requests. Ferran himself will ultimately approve every single stagiaire. If you make the cut, you will be contacted - by the end of December/beginning of January. If you don't, you won't.
One of the legendary stories at El Bulli is about a Japanese guy - Tomo-san - who sent Albert an email every single week - for three years. He finally got in - just this past season.