LEMON BUTTER COOKIES
2 sticks (8 ounces) unsalted butter, at room temperature
2/3 cup confectioner's sugar, sifted
2 egg yolks, at room temperature
Pinch of salt
2 teaspoons pure vanilla
Grated zest of 1 to 1 1/2 lemons, to taste
2 cups flour
1/2 cup sugar for coating
Put the butter in the bowl of a mixer fitted with the paddle attachment and beat at medium speed until smooth. Add confectioner's sugar and beat until smooth and silky. Beat in 1 egg yolk, the salt, vanilla and lemon zest. Reduce speed to low and add the flour, beating just until it disappears. It is better to under-beat than over-beat. If the flour isn't completely incorporated, blend it in with a rubber spatula. Turn the dough out onto a counter, gather it into a ball and divide in half. Wrap each half in plastic and refrigerate for at least 30 minutes. Form each piece of dough into a log about 1 to 1 1/4 inches thick, wrap in plastic and chill for 2 hours. (Wrapped airtight, the dough can be refrigerated for up to 3 days or frozen for up to 1 month.)
Position rack to divide oven into thirds and preheat to 350 degrees. Line 2 baking sheets with parchment paper. While the oven is heating, prepare the sugar coating. Whisk the remaining egg yolk in a small bowl until smooth and liquid enough to use as a glaze. Spread the granulated sugar on a piece of waxed paper. Unwrap the logs of dough and brush them lightly with egg yolk. Roll the logs in the sugar, pressing gently to get it to stick. With a sharp, slender knife, cut logs into cookies about 1/4 inch thick. Place on lined baking sheets, leaving about 1/2 inch between cookies.
Bake cookies for 12 to 14 minutes, switching top and bottom sheets about halfway through baking time, until set but not browned. (It's fine if the yolk- brushed edges brown a smidgen). Transfer to a rack and cool to room temperature. Yields 50 cookies
Keeping: Packed airtight, the cookies will keep for 5 days at room temperature.
These cookies do not freeze well.