Cream butter. Add sugar and beat until light and fluffy. Beat in eggs and vanilla. Gradually add flour, mixing thoroughly; stir in nuts. Divide dough in half. Pat 1/2 of dough evenly into lightly buttered 9 inch square baking pan. Spread jam evenly over dough. Drop remaining dough by tablespoons over jam. Press lightly to form top layer of dough and cover most of the jam. Bake in preheated oven at 325 degrees for 1 hour. Cut into 6x6 inch bars. Makes 36 cookies.