Open the vodka and remove the plastic pouring spout, if it has one.
Cut the vanilla beans in half and then slice them down the middle to split them. Using a sharp knife, gently scrape the seeds out of the pods. Scrape the blade of the knife with the seeds on it onto the rim of the vodka.
Once the vanilla pod is scraped clean, run it around the rim of the bottle to knock the seeds down. Continue to do this to the rest of the vanilla beans.
Give the vodka a shake and store in a cool place. Let the vanilla beans infuse into the vodka for at least six months. Occasionally shake the bottle. When the extract is ready it will be a light brown and very fragrant.