- Portion size 12 servings
Line 2 large rimless baking sheets with parchment paper; set aside.
In bowl, beat butter with icing sugar until fluffy. Beat in egg and vanilla. Press flour, cocoa and salt through fine sieve set over separate bowl. Repeat once or twice, until mixture is evenly coloured. Stir into butter mixture in 2 additions to form smooth fairly soft dough.
Divide dough in half. Shape each half into 8-inch (20 cm) log. Wrap in plastic wrap and chill until firm enough to square off sides and shape into straight-sided log, about 1 hour. Rewrap and refrigerate until firm enough to slice, about 3 hours.
Cut into 1/8-inch thick slices; place about 1 inch apart on prepared baking sheets. Bake in top and bottom thirds of 375F (190C) oven, switching and rotating pans halfway through, until wafers are just firm to the touch and slightly darkened, about 9 minutes. Let cool on pan on rack for 2 minutes; transfer to rack and let cool completely. (Make-ahead: Layer between waxed paper in airtight container and store at room temperature for up to 2 days or freeze for up to 2 weeks.)
In small bowl, stir vanilla with instant coffee granules until dissolved; set aside. Beat whipping cream with sugar until stiff peaks form; blend in vanilla mixture.
Divide wafers into 5 batches. Arrange 1 batch in single layer on flat cake plate. Cover with about one-sixth of the whipped cream mixture. Add second layer of wafers and cream. Repeat until all wafers are used. Cover top and sides of cake with remaining whipped cream.
Drape lightly with plastic wrap and refrigerate until wafers are tender, about 6 hours. (Make-ahead: Refrigerate for up to 2 days.)
Garnish with chocolate-covered espresso beans.