Beat together the butter, sugar and egg yolks until the mixture is smooth. Stir in the flour until it is well blended. Break off small pieces of dough and press them into 1" tart or hors d'oeuvre pans, (or mini muffin pans) forming a shell about 1/8" thick.
To make the filling, combine the pecans, powdered sugar, vanilla, and egg white, in a bowl. Beat until the mixture is well blended.
Spoon enough of the filling into each of the cups to come level with the edge of the shell.
Bake at 350 for 20 minutes, or until the filling is lightly browned. Transfer pans to wire rack and cool for 5 minutes.
Carefully remove cups from the pan, cool completely.
Makes about 4 1/2 dozen cookiesRecipe submitted by Penny on 10/1/00