In a large mixing bowl, cream the butter, shortening and sugar. Beat in egg and vanilla. Combine the flour, salt, baking powder and baking soda; gradually add to creamed mixture alternately with sour cream. Mix well. Shape into 1-1/4-in. balls; roll in nuts.
Place 2 inches apart on greased baking sheets. Using the end of a wooden spoon handle, make a 3/8- to 1/2-in.-deep indentation in the center of each ball. Fill with jam. Bake at 350° for 10-12 minutes or until lightly browned. Remove to wire racks.