Defrost a bag of frozen cooked chestnuts.
Combine 4 cups of whole milk and 2 cups of chestnuts into a sealable container and refrigerate overnight
Pour the mixture (with the whole chestnuts) into a blender and blend until you have a puree looking mush
Strain through a fine-mesh sieve to discard all the solids
Add 4 oz of agave syrup to sweeten the milk and bring the chestnut flavor even further out. When refrigerated, this milk will keep good for up to a week or so.