1 cup (8 ounces/226 grams) unsalted
butter, at room temperature
1⁄3 cup (22⁄3 ounces/75 grams) sugar
1⁄2 teaspoon salt
1⁄3 cup (22⁄3 ounces/75 grams) packed
light brown sugar
1 large egg
11⁄2 teaspoons vanilla extract
Preheat the oven to 300°F.
Put the walnuts on a baking sheet and toast until golden and fragrant, about 6 minutes,
stirring once. Remove from the oven and cool completely.
Sift the flour, baking powder, and baking soda together and set aside.
Put the butter, sugar, salt, and 1⁄2 cup of the walnuts in the bowl of an electric mixer
fitted with the paddle attachment. Beat on medium speed, scraping down the sides
of the bowl once or twice, until the walnuts break up and the mixture is light and fluffy,
about 5 minutes. With the machine running, add the egg and then the vanilla, mixing
until fully incorporated. Turn the speed to low and add the flour mixture, mixing just until no traces of flour remain. Cover the bowl and refrigerate for at least 4 hours,
or up to 3 days.
When ready to bake, preheat the oven to 325°F. Line two baking sheets with parchment
paper.
Form the dough into 1-inch balls and put 2 inches apart on the baking sheets. Use your
palm to flatten each ball slightly, and gently press a walnut half into the center of each
cookie. Bake until lightly golden brown, about 10 minutes. Transfer to a cooling rack to
cool completely. The cookies can be stored in an airtight container for up to 3 days
