Preparation

• Position a rack in the center of the oven, and heat the oven to 350°F. In a medium bowl, whisk the flour and salt. In a stand mixer fitted with the paddle attachment (or in a large bowl using a hand-held mixer), beat the butter and walnuts on medium speed until very soft and light, about 3 minutes. Beat in the confectioners’ sugar and vanilla until thoroughly combined, about 1 minute. Scrape the bowl with a rubber spatula. With the mixer on low speed, slowly blend in the flour until incorporated, about 30 seconds.
• Using your hands, roll the dough into 1- to 1-1/4-inch balls, and set them about 2 inches apart on ungreased cookie sheets. Press your thumb into the middle of each dough ball to create a well for the preserves. Stir the preserves to loosen, and then spoon about 1/2 tsp. into the middle of each. Bake until the cookies are golden brown, about 20 minutes. Let the cookies cool on the sheet for 1 minute before transferring to a cooling rack. Store in an airtight container for up to 4 days.