Split one vanilla bean in half and scrape the seeds from each half. Cut the two halves into about 1/2" pieces. Add the pieces and the seeds to three cups of white sugar in a glass jar. Tightly close and store for one week, shaking occasionally. Sieve the sugar as you use it, returning the beans and seeds to the jar. This may be repeated over and over for 6 months or so, until the flavour weakens.