Hazelnut-Mocha Dacquoise

Position racks in the upper and lower thirds of the oven and preheat to 325 degrees F.

Spread the hazelnuts on a baking sheet and bake until toasted, 12 to 15 minutes; let cool completely.

Combine 1 cup each hazelnuts and sugar and the potato starch in a blender or food processor and pulse until very finely ground.

Transfer to a large bowl.

Reduce the oven temperature to 275 degrees F. Line 2 large baking sheets with parchment paper. Using a bowl as a guide, draw three 7-inch circles on the parchment with a pencil (2 circles on 1 piece and 1 circle on the other); flip the parchment so the markings face down.

Put the egg whites, 1/2 cup sugar and the salt in a large heatproof bowl. Set over a saucepan of simmering water (do not let the bowl touch the water) and whisk until the sugar is dissolved and the mixture is warm, 2 to 5 minutes.

Remove the bowl from the saucepan and beat with a mixer on medium-high speed until stiff and shiny but not dry, about 2 minutes.

Fold the milk and one-quarter of the egg white mixture into the nut mixture with a rubber spatula until smooth, then fold in the remaining egg whites until just combined. Divide the batter among the 3 circles on the parchment and spread evenly with an offset spatula to fill the circles.

Bake 1 hour, 30 minutes, then switch the position of the pans and continue baking until firm, dry and golden, 1 to 2 more hours. (The layers are done when they easily peel off the parchment.)

Let cool slightly on the baking sheets; peel off the parchment and transfer to a rack to cool completely.

Meanwhile, make the ganache: Put 1 cup cream in a microwave-safe bowl; microwave until very hot, about 2 minutes.

Whisk in the chocolate and espresso powder until smooth.

Combine the remaining 4 cups cream and 1/3 cup sugar in a large bowl and beat with a mixer on medium speed until it barely holds soft peaks, 1 to 2 minutes. Finish beating the cream by hand with a whisk until soft peaks form; do not overbeat.

Put 2 meringue layers on a baking sheet; spread half of the ganache on each, to the edge. Refrigerate until set, 15 minutes. (If the ganache is too firm to spread, microwave in 20-second intervals to soften.)

Place one of the ganache-topped meringues on a platter.

Spread with 1 cup whipped cream. Stack the other ganache-topped meringue on top; spread with another layer of whipped cream. Top with the last meringue, then cover the top and side of the cake with the remaining whipped cream. Chop the remaining 1/3 cup hazelnuts and sprinkle on top of the cake along with the shaved chocolate. Refrigerate at least 6 hours or overnight before serving.

Photograph by Con Poulos