Combine the butter, cream cheese, sugar and vanilla in a large mixing bowl. Beat with an electic mixer for about one minute at medium speed. Add the flour and salt. Beat again to mix well. Divide the dough into 4 or 5 pieces. Wrap each piece in waxed paper or plastic wrap and chill in the refrigerator for about 2 to 3 hours.
Spray several large cookie sheets with non-stick cooking spray; set aside. Remove the chilled dough from the refrigerator, one piece at a time. Roll 1/2 piece at a time on a floured pastry cloth to about 1/8" thick. Cut the rolled out dough with a 2 to 2-1/2" round cookie cutter. Arrange the unbaked, cut out cookies, about one inch apart, on the prepared cookie sheets. Top the center of each unbaked cookie with a small amount of jam (1/4 to 1/2 tsp,). Fold the edges of dough to the center to form the shape of a lily flower. Press together slightly to seal on one end. (The cookies should be cone shaped with jam showing on the wide ends.) Bake in a preheated oven at 375º for 8 to 10 minutes or until very lightly browned. Cool on wire racks.
To store the baked cookies - cool completely. Arrange in a can or tightly covered container with waxed paper or plastic wrap between layers to keep the cookies from sticking together.