Imagine if guacamole were blended with salsa verde and pesto. That is what this magic green sauce reminds me of. It can be scooped with corn chips or tortilla chips, used as a sauce with grilled fish, as a spread for a sandwich, a topping for tacos and more or thinned out a bit to make a salad dressing. It's sheer utilitarianism is astounding. For three days, we used this sauce with every meal. David even added some to his omelette one morning. It never turned brown and tasted good until the last spoonful. And that makes it even more magical.
Place all ingredients--except the pistachios or other nut of choice--in a food processor and pulse until thoroughly blended.
Add pistachios and pulse until mostly smooth.
Serve as a dip, spread, salad dressing base or sauce. To turn it into a salad dressing or marinade, add a little water or oil to thin it out. Refrigerate any leftovers and use within 3-4 days.