Preparation

• In a medium mixing bowl, combine the flour, baking powder, and salt. Whisk until well blended.
• In the bowl of a stand mixer fitted with the paddle attachment (or in a large mixing bowl with a hand mixer), beat the butter and sugar on medium speed until fluffy and well blended, about 3 minutes. Scrape down the bowl and the beater. Add the egg, egg yolk, and vanilla. Continue mixing on medium until well blended, about 1 minute. Add the flour mixture and mix on low speed until the dough is well blended and forms moist clumps, about 1 minute.
• Gently knead the dough by hand in the bowl until smooth. Shape it into two square or round logs, each about 10 inches long, and wrap in plastic wrap. Refrigerate until chilled and very firm, about 4 hours.
• Position a rack in the center of the oven and heat the oven to 350ºF. Line two or three cookie sheets with parchment or nonstick baking liners.
• Using a thin-bladed, sharp knife and a ruler, mark off 3/16-inch-wide slices on the top of the log. Using the same knife, cut straight down to form cookies. Arrange the cookies about 1 inch apart on the lined cookie sheets. Bake one sheet at a time until the cookies’ edges are golden brown, 11 to 13 minutes (for even browning, rotate the sheet after about 5 minutes). Let the cookies cool on the sheet for about 10 minutes and then transfer them to a rack to cool completely.

Make Ahead Tips

The dough logs may be refrigerated for up to 3 days or frozen for 1 month. Thaw overnight in the refrigerator before proceeding with the recipe.

Ginger-Spiced Slice & Bake Cookies:Add to the flour mixture: 3/4 cup finely chopped crystallized ginger, 2 tsp. ground ginger, 1 tsp. ground cinnamon, and a pinch of ground black pepper. The crystallized ginger may cause the dough to crumble as you slice the cookies; just press them back together.