Be sure to use a high power blender - this must be completely smooth although a few pieces of pistachio are ok and can add a bit of texture. If you prefer this, add the pistachios after you have blended the whites to completely smooth. Then blend in the pistachios to your desired consistency. This tastes better after an overnight rest in the refrigerator.
Lightly scramble the egg whites in a large nonstick pan over medium heat until just set. Set aside to cool for a few minutes. (You can also cook them in a microwave-safe glass bowl in the microwave - just microwave on high and check after a few minutes - they cook quickly once they turn opaque and begin to solidify.)
Break up the egg whites and transfer them to a blender. Add remaining pudding ingredients and blend until completely smooth, adjusting salt, vanilla, and sweetener, as desired. Add more cashew milk, if desired but the pudding will thicken a bit as it sits. Divide between 2 serving dishes and refrigerate overnight.
Notes
Protein:Energy Quotient [calories]: 1.56, Protein % of calories: 50.9%