In a food processor, process butter, confectioners sugar and salt until smooth. Add flour and pulse until dough forms. Stir in pistachios.
Shape the dough into 8" long logs, tightly wrap in plastic and refrigerate for at least 3hours. Logs can be frozen for up to 1 month.
Preheat oven to 350°F. Cut dough into ¼ inch slices and transfer to parchment lined baking sheets. Bake until cookies are set and barely golden at edges, about to 10-15 minutes, rotating sheets half way through. Let cool completely on wire racks.
Once the cookies are completely cooled, spread ½tsp strawberry jam on bottoms of half the cookies, then sandwich with the remaining cookies.
Store in airtight container for up to 1 week.