White-chocolate espresso shortbread icebox cookie. (Photo, Sian Richards.)
1 1/2 cups
, at room temperature
STIR flour with white chocolate, instant espresso powder and salt in a medium bowl.
BEAT butter with sugar in a large bowl, using a wooden spoon, until smooth, 1 min. Gradually stir in half of flour mixture, until just combined. Add remaining flour mixture, kneading with your hands, until dough forms a ball.
DIVIDE dough in half, then roll each portion into a 2-in.-wide log. Wrap each log in waxed paper and twist ends. Chill until firm, 2 hours.
PREHEAT oven to 350F. Position racks in top and bottom thirds of oven. Line 2 baking sheets with parchment.
SLICE cookies into 1/4-in. rounds and arrange 2 in. apart on prepared sheets. Cookies will spread as they bake.
BAKE in top and bottom thirds of oven, switching sheets halfway through, until lightly golden, 15 to 19 min. Leave on sheet for 5 min, then transfer cookies to a rack to cool completely. Repeat with remaining dough.