Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, cream the softened butter and powdered sugar until light and fluffy.
Add in the vanilla extract and mix until well combined.
Slowly add the flour, salt, and finely ground pistachios to the butter mixture, stirring until a soft dough forms.
Roll out the dough on a floured surface and cut into rounds using a cookie cutter. Place them onto the prepared baking sheet.
Bake for 12-14 minutes or until the edges are lightly golden. Let cool completely on a wire rack.
For the pistachio cream filling, beat the heavy cream, pistachio butter, powdered sugar, and vanilla extract together until soft peaks form.
Once the cookies are cooled, spread a dollop of the pistachio cream filling on the bottom of one cookie, then sandwich with another cookie.
Garnish with chopped pistachios, if desired, and refrigerate to set the filling for at least 30 minutes before serving.