3bottlesVodka 35-40% alcohol 750 ml each (70-80 proof)
Bring a large stock pot of water to a full boil over high heat. Place a large absorbent dish towel over a work surface. Using grippy tongs or a canning lifter, submerge the bottles, one at a time, in the water. Let the bottle stay in the water for 10 seconds, then remove with tongs, allowing the water inside the bottle to pour back into the pot. Place the bottle on the dish towel to dry; Repeat with remaining bottles. After the bottles are done, sanitize all the caps in the water at once. Remove them with a slotted spoon and let them dry on the towel. Let the bottles cool before using.
Split each vanilla bean lengthwise with a small sharp knife. Place 2 or 3 split beans in each sanitized bottle (The Kitchn suggests 3 to 5 beans per 8 ounces of vodka, and I've found that 3 beans per 5 ounces of vodka usually yields a nice, strong result that is obvious in baked goods).
Fill each bottle with vodka using a measuring cup with a pour spout. Screw the bottle caps on tightly. Place the bottles in a cook dark place and shake them about once a week for 2 months or longer.
You can cap the bottles with wax right after they're bottled, or you can wait until closer time for gifting. I'm in favor of doing this early, because the holidays are always so busy. Here's how you do it.
Place a small length of filament tape around the bottom edge of the bottle cap, so that the tape covers the gap between the bottle cap and the bottle neck. Fold the end of the tape back onto itself to create a pull tab. Repeat with all the bottles.
Melt the sealing wax in your smallest saucepan or use a metal (heatproof) 1 cup measure. You could also use a butter warmer with a tea light underneath but this will take much longer for the wax to melt (also see my disposable mini pie pan recommendation in this post). When the wax is melted (at approximately 160 to 170 degrees F), remove from heat. Pour the wax into a small, deep container. Dip the bottle caps into the wax past the filament tape pull-tab. Lift the cap and allow the excess wax to drain; dip again. Turn the bottle upright immediately for drippy effect, and immediately place a wax stamp on top of the bottle cap, if using. For non-drippy effect, hold the wax-dipped bottle over the container until all the wax has dripped off. When the wax stops dripping, turn the bottle upright.
Label the bottles, or decorate them with washi tape, if desired.
Steep for 3 months in a cabinet or other dark place. Shake occasionally during steeping time.
Vanilla extract will keep at room temperature indefinitely.
Some varieties of vanilla beans will macerate more quickly than others, meaning the color of your extract may be lighter than my result at the end of 3 months. This doesn't mean the product isn't ready to use. If you'd like to achieve the darkest color possible, here are some options.
Chop the vanilla beans into little pieces. This will make them break down more quickly.
Split the vanilla beans then remove the seeds. Funnel them into the bottles and then add the vanilla bean pods. Shake.
You can also 'cheat' and buy a bottle of pure vanilla extract (that is dark in color) and add 1 teaspoon to each homemade bottle to darken the liquid.
All of this is an easy way to gain some color, but your vanilla extract won't be ready to use until it's had enough time to infuse, which is about 3 months.