Cream the butter and powdered sugar, then beat in the egg and vanilla.

Mix in both flours and salt until a dough forms, then chill 30 minutes.

Roll dough to 1/4 inch and cut rounds; cut a small window from half of them.

Bake at 350F for 10 to 12 minutes until edges are lightly golden, then cool completely.

Dust the cut-out tops with powdered sugar.

Spread jam on the solid bottoms and gently sandwich with the window tops.