Slice each vanilla bean lengthwise to expose the tiny seeds. Place the vanilla beans in a clean glass jar with a tight-fitting lid. Pour the vodka over the beans, ensuring they are completely submerged. Seal the jar tightly and shake gently. Store in a cool, dark place for at least 8 weeks, shaking gently once a week to help extract the flavors. The vanilla extract will develop a rich aroma over time and can be used for baking or desserts.