TIRAMISU COOKIES

Steps:

• Preheat oven to 350 degrees. Line 2 baking sheets with parchment paper.
• Using a mixer with the whisk attachment, beat yolks and 1/2 cup granulated sugar until pale and stiff, about 3 minutes. Add espresso powder, and beat for 2 minutes. Add flour, and beat until just combined. (Mixture will be very thick.)
• In a clean bowl, using a clean whisk attachment, beat whites and salt on medium speed until foamy. With the machine running, add remaining 1/2 cup granulated sugar in a slow stream, beating until stiff peaks form, about 5 minutes. Fold whites into yolk mixture in 3 additions until well combined.
• Using a pastry bag fitted with a 1/2-inch plain tip (such as Ateco #806), pipe batter onto baking sheets into 60 lines that are 2 inches long and 1 inch wide, spacing 1 inch apart. Dust with cocoa.
• Bake, rotating sheets halfway through, until firm, 12 to 14 minutes. Let cool completely on parchment on wire racks. (Cookies can be stored for up to 3 days.)
• Stir together mascarpone, confectioners' sugar, liqueur, and vanilla until well combined. Cover, and refrigerate for 15 minutes (or up to 3 days).
• When ready to serve, brush the cookies' flat sides with melted chocolate. Refrigerate, flat side up, until chocolate is firm, about 10 minutes.
• Spread a generous 1/2 teaspoon mascarpone filling over chocolate side of half of the cookies. Sandwich with remaining cookies. Serve immediately.