Combine the apple cider, cinnamon sticks and cardamom pods in a wide-mouthed pot and bring the cider to a boil over medium-high heat. Reduce to a simmer and continue to simmer until the cider is reduced to 1 cup of liquid, about 30 minutes.

Strain out the cinnamon and cardamom, and return the liquid to the pot. Add the agave nectar and return the liquid to a boil over high heat. Bring the liquid to 218 degrees F, using a candy thermometer to confirm the temperature.

Remove from the heat and allow to cool slightly before pouring into a jar.