Wash the sassafras and sarsaparilla and strain. Repeat 4 times. Place the barks, orange peel, lemon peel, lime peel, ginger, cinnamon, cloves, star anise, juniper berries, and water in a medium-sized pot. Bring mixture to a boil and simmer for 40 minutes uncovered. Turn off heat. Add the nutmeg, molasses, sugar, and vanilla extract and stir until sugar dissolves completely. Strain ingredients through a metal mesh strainer and quickly cool mixture in an ice bath. Once cooled, strain again through a double layer of cheese cloth into a keg or whipping siphon. Pressurize and refrigerate for at least 3 days to carbonate.