Drain the juice of crushed pineapple but save 1 tbsp. In a bowl, stir Pistachio pudding mix and crushed pineapple.
Then the cottage cheese.
Then the Cool Whip topping.
Add the reserved pineapple juice.
Stir in half of the walnuts.
Then the mini-marshmallows. Cover the bowl and chill in the fridge until ready for serving.