Walmart is selling a Pistachio nut butter from Italy in their peanut butter area, at least in my area. Its great on toasted bread. I imagine you could use something to thicken it and use it for a cookie filling. (Bettergoods is the brand.)
Pistachio butter is good on toast, or as a base for creamy salad
dressings and sauces, and in ice cream, cookies, and chocolate confections.
Some cultures use it in savory dishes like pesto,
crostini toppings, or as a sauce for pasta and vegetables.
Sprouts also sells Pistachio nut butter that has not been sweetened.
I thought about this when you posted your pistachio shortbread cookies recipe! Thank you!