In large bowl of an electric mixer, beat butter and granulated
sugar until creamy; beat in vanilla extract. Gradually add pecans
and flour, blending thoroughly. Cover tightly with plastic wrap
and refrigerate until easy to handle (1 to 2 hours) or for up
to 3 days.
On a floured board, roll out dough to a thickness of 1/8-inch.
Cut out with a 2-inch heart-shaped cookie cutter and transfer
to ungreased baking sheets, spacing about 1 inch apart. Cut
out a hole in center of half of the cookies, using a tiny round
cutter about 1/2 inch in diameter (you can use the cap from
a vanilla extract or other extract bottle).
Bake in a 375 degrees
F oven for about 12 minutes or until lightly browned.
Transfer to racks and let cool completely.
Sift confectioners' sugar over tops of cookies with holes;
then spread bottom sides of remaining cookies with jam. Place
a sugar-topped cookie on each jam-topped cookie to form a sandwich.