Lemon Butter Cookies (Sables au Citron)

In the bowl of a mixer fitted with the paddle attachment, beat the butter at medium speed until it is smooth. Add the sifted powdered sugar and beat again until the mixture is smooth and silky. Beat in 1 yolk, followed by the salt, vanilla and zest.

Reduce the mixer speed to low and add the flour, beating just until it disappears. It is better to under-beat than over-beat at this point; if the flour isn't fully incorporated, that's OK, just blend in whatever remaining flour needs blending with a rubber spatula.

Turn the dough out onto a counter, gather it into a ball, and divide it in half. Wrap each piece in plastic wrap and refrigerate for about 30 minutes.

Working on a smooth surface, form each piece of dough into a log that is about 1 to 1 1/4 inches thick. Wrap the logs in plastic and chill for 2 hours. (The dough can be wrapped airtight and kept refrigerated for up to 3 days or stored in the freezer or up to 1 month.)

Position the racks to divide the oven into thirds and preheat the oven to 350 degrees F. Line 2 baking sheets with parchment paper.

While the oven is preheating, whisk the remaining egg yolk in a small bowl until it is smooth and liquid enough to use as a glaze. Spread the sugar out on a piece of wax paper.

Remove the logs of dough from the refrigerator, unwrap them, and brush them lightly with a little egg yolk. Roll the logs in the sugar, pressing the sugar gently to get it to stick if necessary, then, using a sharp slender knife, slice each log into cookies about 1/4 inch thick. (You can make these thicker if you'd like; just bake them longer.)

Place the cookies on the lined baking sheets, leaving about 1/2 inch space between them. Bake the cookies for 12 to 14 minutes, or until they are set but not browned. (It's fine if the edges brown a smidgen.) Transfer the cookies to cooling racks to cool to room temperature.

Packed airtight, the cookies will keep for about 5 days at room temperature. Because the sugar coating will melt, these cookies are not suitable for freezing.

NOTE: I've made these tender, sweet cookies at Christmas time and dolled them up by rolling them in larger-grained sugar. They're fun rolled in crystal sugar, which gives them a bit of crunch. You could even roll them in colored sugar to add dash to a tin of assorted cookies.

Recipe Source: "Paris Sweets" by Dorie Greenspan