(**NOTE: be sure to allow time for dough to be refrigerated.)
In a bowl, mix butter, cream cheese, vanilla and sugar, and beat with mixer until fluffy. Stir in flour and salt until a soft dough is formed. Cover and refrigerate 2-3 hours.
Preheat oven to 350. Spray cookie sheet with cooking spray, set aside. Roll dough to 1/8" thickness on lightly floured board. With a cookie cutter, or glass (i use a glass jar), cut dough into 3" rounds.
Place 1/4 tsp. of jam in center, fold in half and crimp edges with a fork.
Pierce top of each cookie with a sharp knife for steam release. Arrange cookies on greased sheet.
Bake 10-12 minutes, until cookies are lightly browned. Cool on wire rack.