(If you need to wash your molds, wash in clear hot water. DO NOT use soap. Dry thoroughly.)

Cream butter and sugar at low speed. Add egg yolk and vanilla. Continue to beat until smooth. Add flour and continue to beat at low speed. Dough will seem very dry, but will moisten as it is mixed. Gather dough into a ball. Wrap in plastic wrap and chill for one to two hours.

Meanwhile:
Using a pastry brush, lightly oil your cookie mold with vegetable oil. Blot out the excess oil with paper towel, as much as possible.

Dust with flour, as you would a cake pan. Tap the edge of the mold on a cutting board to remove any excess flour. You will have to re-flour before each cookie, but DO NOT re-oil it.

Take a piece of dough and press it firmly and evenly into the mold. Trim off any excess dough with a serrated bread knife. Or–I’ve found that I can put the dough on the mold and roll with my rolling pin for a nice smooth back and more evenly distributed into mold, without excess thickness on the back.

To give your cookie a nice edge, trim, then pull the dough back slightly from the edge of the mold with finger.

Holding the mold upright, sharply tap edge on a protected surface (a cutting board covered with a folded dish towel works well) three times or until dough starts to fall out. Catch dough with hand and transfer to a baking stone. If the dough does not fall out, rotate the mold and strike again 2 or 3 times.

Bake cookies in a preheated 350-degree oven.