How to Make It
Combine pistachios and 3 cups water in a bowl; let stand at least 8 hours or overnight. Drain. Process nuts, agave nectar, and 2 1/2 cups water in a blender until very smooth, about 3 minutes. Pour mixture through a strainer lined with 2 layers of cheesecloth into a bowl; discard solids (or reserve for another use). Store, refrigerated, for up to 1 week.