1) Butter a large surface. Cook the sugar, syrup and water until the mixture thickens and bubbles (about 110C). Add the tablespoon of butter and the pecans. Stir continuously and continue cooking until nuts begin to brown or start popping (145C).
2) Remove from the heat. Add the vanilla and soda and stir thoroughly. Pour quickly in several pieces on the large buttered surface. Do not spread with a knife or spoon.
3) Allow to cool slightly and then stretch and pull with your hands until very thin (the thinner it is stretched, the more brittle it will be).
4) When the brittle is cooled and hardened, break into small pieces. Store in an airtight container.