Italian for "lady's kisses," these little sandwich cookies layered with dark chocolate are a perfect accompaniment to an after-dinner espresso.
Preheat oven to 350 degrees. Beat 7 tablespoons butter with sugar on medium-high speed until light and fluffy, about 3 minutes. Add vanilla and zest, then both flours and salt; beat until a dough starts to form. Transfer to a work surface; knead until a firm dough forms, 1 minute.
Scoop 1 level teaspoon of dough; roll into a ball. Place on a rimmed baking sheet lined with parchment. Repeat with remaining dough, spacing balls 1 inch apart. Freeze until firm, 15 minutes.
Meanwhile, melt chocolate and remaining 1 tablespoon butter in a heatproof bowl set over a pan of simmering water. Let cool until thick and spreadable, 20 minutes.
Bake cookies until domed and light golden, about 16 minutes. Let cool completely, about 45 minutes. Spread 1/2 teaspoon chocolate mixture on flat side of one cookie; sandwich with flat side of a second. Repeat with remaining cookies. Let chocolate set before serving. Cookies can be stored in an airtight container at room temperature up to 3 days.