Apologies for the delay in posting this--was offline preparing for, then having, then recovering from, annual holiday party.
In my opinion these are the best cookies in the world. I like to have a log of the dough in my freezer at all times, in case of emergency. I've adapted the recipe a bit from one by Dorie Greenspan that I saw in the NYTimes mag last year.
8 oz butter, at room temp (unsalted or, my own pref, the cultured butter made by the Vermont Butter and Cheese Co, which is "lightly salted"; I still add salt when using this)
1/2 c sugar
1/4 c sifted confectioners' sugar (sift before measuring)
Generous 1/2 t kosher salt
2 large egg yolks, at room temp
2 c AP flour
Grated zest of 2 lemons
Optional decoration (I always do this):
1 egg yolk, beaten
Put the sugar in a small bowl and add the lemon zest. With your fingers, rub the zest and sugar together rather vigorously. The mix will be damp and very aromatic. Cream butter in mixer with paddle attachment until extremely smooth. Add the sugar/zest mix, confectioners' sugar and salt and continue to beat until smooth and velvety, about a minute. Reduce speed to low and add the egg yolks (not including the one used, if you wish, for decoration), and mix until well-blended.
Stop the mixer and add the flour. Drape a towel over the bowl and pulse a few times until flour is integrated into the dough enough that it does not fly all over the kitchen while the mixer is running. Mix on low speed just until flour is absorbed, about 30 seconds. If there's some flour in the bottom of the bowl, mix it in with a rubber spatula. The dough will be soft and clumpy.
Gather it into a ball and divide it in half. Shape each piece into a log on a piece of parchment, then roll the parchment around the log and wrap it well in plastic. The original recipe says to make the dough about 9 inches long, but I like small cookies so I make it thinner and longer. Refrigerate for at least 2 hours, up to 3 days, or freeze.
When ready to bake, line a couple of sheets with parchment and preheat oven to 350. If you want to decorate the edges of the cookies (they are rather plain-looking otherwise) brush the log with the beaten egg yolk and sprinkle the whole thing generously with sugar (I like yellow sparkle sugar). Slice into rounds (the recipe says these should be 1/3" thick but I do thinner, smaller ones--less than 1/4"--to good effect). Bake, one sheet at a time, for about 18 minutes, rotating the sheet halfway through, until cookies are lightly browned around the edges (though I find the slightly overdone ones to be very tasty).
I hope you enjoy these as much as I do. Happy holidays!