When you have some free time, perhaps while watching TV, remove shells and as much of the skin as you can from the pistachios.
OPTIONAL: Place pistachios in the strainer and rinse salt off. If you prefer your pistachio butter to be saltier, skip ahead to step 4.
Once rinsed pay dry to remove excess salt and salty water you don't want in your nut butter.
Put pistachios in the food processor or blender.
Process on high until pistachio look grainy.
Using 1 to 4 tablespoons at a time, add water and continue blending. It's best to slowly add water and blend to reach your desired consistency, one that is not to watery.
Repeat step 6, adding water and blending as needed. Scrap sides of the food processor or blender occasionally and continue processing/blending until smooth.
Here's the pistachio butter after slowly adding the water and processing.
Once you reach your desired smoothness/consistency put nut butter in a glass jar and store in the refrigerator. Enjoy as you would any other nut butter.