One of the things I like most about Cook's Illustrated (aside from the fact that their recipes generally work) is that they explain their process of testing the recipes and how they arrive at the final version, including why they use certain ingredients or a particular method. I've picked up so many little tidbits here and there that have helped me to become a better baker and cook. When I decided to make these cookies, I started by reading through the recipe and when I saw that it called for including a fully cooked egg yolk in the dough, I was especially grateful that I could go back through the article preceding the recipe to understand why. Otherwise, it probably would have been the sort of question that sent me running to Google to search for an answer. Best I can recall, I've never hard boiled an egg and included its yolk in my cookie dough!
It turns out that cooking the egg yolk before adding it helps to eliminate moisture in the dough to achieve a sandy, crumbly cookie. I loved the texture (as well as the flavor!) of the baked cookies - they reminded me of delicate shortbread cookies - so I'll gladly go to the trouble of cooking the egg next time I make them. What I'm still a bit skeptical about, however, is whether it's really necessary to press the yolk through a fine-mesh strainer before incorporating it into the dough. I'll likely try skipping that step because I found it to be a huge pain and I think I could achieve a similar consistency by mashing the yolk well.
Shaping the cookies into pretzels is a bit more work than just slicing and baking the rounds (which you could also certainly do here) and at first I wasn't sure it was worth the effort. I found, though, that I got into a groove after making my first 5 or 6 pretzels and things started to move more quickly. What really sealed the deal was the cuteness factor after I pulled the first tray of baked cookies from the oven. The sanding sugar provided just a bit of sparkle and since the dough held its shape beautifully in the oven, the cookies looked just like little mini pretzels! This recipe makes a lot of cookies (CI says 80 but I think I was closer to 60) but like most butter cookies, these keep well - about a week in an airtight container.
Vanilla Pretzel Cookies
from Cook's Illustrated
1 large egg
10 tablespoons (1 1/4 sticks) unsalted butter, softened
1/3 cup plus 1 tablespoon (2 3/4 oz) sugar
1/4 teaspoon salt
1 tablespoon vanilla extract
1 1/2 cups (7 1/2 oz) all-purpose flour
1 large egg white, lightly beaten with 1 teaspoon water
4 teaspoons turbinado (or other sanding) sugar
Place the egg in a small saucepan. Cover with 1 inch of water and bring to a boil over high heat. Remove the pan from the heat, cover, and let sit for 10 minutes. Meanwhile, fill a small bowl with ice water. Use a slotted spoon to transfer the egg to the ice water and let stand for 5 minutes. Crack the egg and peel away the shell. Separate the yolk from the white; discard the white. Press the yolk through a fine-mesh strainer into a small bowl.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, sugar, salt, and cooked egg yolk on medium speed until light and fluffy, about 4 minutes, scraping down sides of bowl and beater with rubber spatula as needed. Reduce the mixer speed to low then add the vanilla and mix until incorporated. Stop the mixer; add flour and mix on low speed until just combined, about 30 seconds. Using a rubber spatula, press dough into cohesive mass.
Divide the dough in half; roll each piece into log about 6 inches long and 1 3/4 inches in diameter. Wrap each log in parchment paper and twist the ends to seal and firmly compact dough into a tight cylinder. Chill for 30 minutes.
With racks in the upper and lower thirds of the oven, preheat to 350 F. Line 2 baking sheets with parchment paper. Slice the dough into 1/4-inch rounds, and roll each round into a ball. Roll each ball into a 6-inch rope, slightly tapering the ends. Lift one end and cross it over so that the end rests near the center of the rope to form half of the pretzel shape. Cross the other end of the rope over to form the second half of the pretzel shape. Place the cookies 1 inch apart on the prepared baking sheets. Using a pastry brush, gently brush the cookies with egg white mixture and sprinkle evenly with turbinado sugar.
Bake until the centers of the cookies are pale golden brown with edges slightly darker than centers, about 15 minutes, rotating baking sheets from front to back and top to bottom halfway through. Cool cookies on baking sheet for 5 minutes; using thin metal spatula, transfer cookies to wire rack and cool to room temperature.