How to Make It
Beat butter and sugar at medium speed with an electric mixer until fluffy. Add egg and vanilla, beating well. Add flour, beating just until mixture is blended.
Divide dough into 3 portions; roll each portion on wax paper into a 12-inch log. Cover and chill 8 hours.
Cut each log into 1/2-inch-thick slices; place on lightly greased baking sheets. Press thumb in center of each slice to make an indentation; fill with 1/2 teaspoon preserves.
Bake at 350° for 10 minutes or until edges are lightly browned. Remove to wire racks to cool. Freeze, if desired.