In a blender, purée the water, salt, hazelnuts, cashews, vanilla, agave, and cardamom as smooth as possible (mine had some clumps, as my blender isn't perfect). In a large bowl or glass container, mix the chia seeds with the blended mixture. Stir to combine. Cover and refrigerate overnight or for about 8 hours. Chia seeds will plump up and absorb most of the liquid. Garnish with chopped nuts and dried fruit if you have it.