Make the dough the night before you intend to bake the cookies: Cream the butter and sugar in a mixer until very light-textured, almost white. Separate one egg, reserve white in refrigerator. While the butter and sugar are creaming is a good time to sift the flour and grate the lemon rind. Add one whole egg and egg yolk, vanilla, lemon rind and salt. Add flour.
Chill dough for several hours, preferably overnight. This is important, both because the dough will be unworkable without chilling, and to allow the flavors to blend. It may be refrigerated for several days if necessary.
On the day of baking:
Preheat oven to 375°. Butter two cookie sheets.
Roll very thin on a pastry cloth. (How thin? Experience will tell. Perhaps 2 mm.) Cut out individual cookies with a cookie cutter and place on cookie sheet. Brush tops with reserved egg white, and top each with a pecan. Bake until lightly browned at the edges, about 8 minutes. Watch them like a hawk! Baking time is very dependant on cookie thickness, characteristics of your cookie sheets, and temperature and temperature evenness of your oven.
Cool on wire rack. Makes about 2 pounds. (more…)