Preheat oven to 350 degrees F (175 degrees C). Line 3 baking sheets with parchment paper.
Puree avocado in the bowl of a food processor. Add butter and blend until creamy. Add applesauce, sugar, and milk; pulse to combine. Add egg; pulse until smooth. Add pudding mix, vanilla extract, baking powder, and salt; pulse until dough is smooth and pastel green.
Place pistachio nuts in a resealable freezer bag and crush with a meat mallet. Add crushed pistachio nuts and flour to dough; pulse to combine.
Drop tablespoons of dough 2 inches apart onto prepared baking sheets; flatten gently.
Bake in the preheated oven until bottoms are beginning to brown, about 15 minutes. Remove from oven and cool on baking sheets, 5 to 10 minutes.