To make the chocolate layer: In a blender, process all the chocolate layer ingredients until very smooth. Pour half into another container and set aside. Divide the remaining smoothie mixture between two glasses.
To make the nut butter layer: Blend the nut butter layer ingredients until very smooth, and divide between the glasses. Spoon this on top of the chocolate layer, being careful not to blend the two layers too much. Then, gently add the remaining chocolate layer mixture.
This is beautiful when made in three layers, but is just as delicious if made in two.
Top with chopped almonds and/or cacao nibs, if using.