If you buy skinless pistachios, then you can definitely skip this step. It's going to cost more, but I guess it saves you this step.
The pistachios that I bought still have skins. To get a vibrant green pistachio paste, you want to remove the skin. The skin turns the paste brownish- green
Place pistachios in a heat-proof bowl and pour some really hot boiling water, enough to cover the nuts. Let them soak for 3 minutes
Discard the soaking liquid and then rinse with fresh cold water. Spread them out on a clean kitchen towel or absorbent paper towel.
You can rub the skin off. This is probably the most time-consuming part of the whole process.
But the skin should come off pretty easily after being soaked
Blend into a paste:
Place the skinless pistachios in a food processor or a blender. Add one tablespoon of water. Process or blend them until you get a smooth consistency. It will turn from whole kernels to being chopped up, then powdery, and then turn into a thick paste. If it's too thick, you can add another tablespoon to get a creamy but still thick consistency. You shouldn't have to add more than 3 tablespoons of water
Storage:
Transfer the paste to a clean container. Store them in a fridge for about a week. They can be kept frozen for up to two months