Add the cacao nibs, vanilla beans, and liquor to a swing-top bottle. Give the bottle a shake. Rest for 2 weeks, shaking periodically.
Alternatively, if you don’t have the patience to wait several weeks, you can use heat to speed the process. Gently heat the cacao nibs, vanilla beans, and liquor in the top of a double boiler for 30–60 minutes. Let cool to room temperature and place in a swing-top bottle.
Strain out cacao nibs and vanilla beans. Pour liquid back into swing-top bottle and discard the nibs and beans. Add 1:1 simple syrup to your bottle. Taste and add more simple syrup for a sweeter liqueur. Rest for an additional 1–2 days before using. It will last on your shelf for a very long time.