Cut 4–6 whole vanilla beans lengthwise with a sharp knife. Using the dull side of the knife, scrape vanilla beans from the pods into an airtight container. Cut the empty pods into 1⁄2-inch pieces and add them to the same container. Pour approximately 1 cup of alcohol over the beans and seeds (just enough to cover them). Use 8 ounces of alcohol per 4–6 beans. Secure jar with tight-fitting lid and shake vigorously. Store at room temp in a cool, dark place for at least 2 months, shaking daily for the first 2 weeks. For the most flavorful extract, let it bloom for 6–12 months before use.