1. In a large bowl, beat together the cream cheese, butter, egg, vanilla, and salt. 2. Add in the powdered sugar, then flour, beating between each addition until a stiff dough forms. 3. Cover  and chill in the refrigerator for 2 hours. 4. Preheat oven to 325 degrees and line a baking pan with parchment paper. 5. Scoop out the dough and form into one-inch balls. Place the cookie balls on the lined baking sheet and make an indention in the center of each cookie with your thumb. 6. Bake in the preheated oven for 12-15 minutes, until cookies are browned on the bottom. 7. Remove the cookies from the baking sheet to a wire cooling rack to cool. When cooled completely, top each cookie with a spoonful of blueberry pie filling.