There were some requests for the dessert recipe I made for Thanksgiving, so here it is. It's one of my favorite special occasion desserts of all time, and it also happens to be gluten-free. It comes from Joanne Chang's first cookbook, Flour. I've made changes to the size and assembly of the cake so that it feeds a crowd and avoids pastry bags of any kind. I also serve it in a baking pan so I don't have to decorate the sides. I was way too stressed out by the piano delivery to do any detail work that afternoon (or ever!).
A dacquoise is a French layer cake made with sheets of nut meringue (egg whites mixed with sugar and ground nuts and baked until crisp). This particular version uses almond and hazelnut meringues layered with espresso buttercream and chocolate ganache. It's like a Napoleon but with nuts and chocolate. It's about as fancy as I ever get. The components aren't hard to make, but the timing of the assembly can be tricky. The meringue slabs have to be fully cooled and half of the ganache should be thick enough to mound while the other half should be thin enough to pour fluidly during the crucial window of time when the buttercream has just come together but hasn't yet broken. This is not to scare you away, but merely to warn you not to make this in a situation where a business deal is on the line unless you enjoy high-octane panic attacks.
A note about meringue: egg whites should be completely yolk-free in order for the recipe to work correctly. Also, make sure the bowl and beaters are clean with no hint of grease. Save one of the yolks for the buttercream below, and then submerge the rest in cold water covered in the fridge to make lime or lemon curd within a few days (recipe in WINTERSWEET, see note on page 151). For the nuts, "blanched" means their dark skins have been removed.
3/4 cup blanched whole hazelnuts, divided
1/2 cup blanched whole almonds
1-1/3 cups confectioner's sugar
1/8 tsp. kosher salt
6 egg whites
1/3 cup granulated sugar
1 pound semisweet or bittersweet chocolate chips
2 cups heavy cream
3/4 cup granulated sugar
1 egg yolk
1-1/2 cups (3 sticks) unsalted butter, at room temperature, cut into thirds
1 Tbsp. instant espresso powder (or 2 Tbsp. instant coffee powder ground fine)
1/4 tsp. kosher salt
Preheat the oven to 300°F. Find yourself a nice-looking rectangular baking dish for serving and set aside. Line two sheet pans with parchment paper and trace three rectangles several inches smaller than the dimensions of the pan you will be serving it in. For example, if using a standard 9x13-inch pan, measure rectangles 6x10 inches. Make sure the rectangles are spaced at least 2 inches apart as the batter will spread a bit. Turn the parchment sheets over so the pencil is on the underside of the paper.
For the meringue layers, toast 1/2 cup of the hazelnuts in a dry sauté pan over medium heat, tossing frequently, until they turn golden in spots and smell toasty, about 3 to 5 minutes. Add the toasted hazelnuts to the bowl of a food processor to cool. Set the remaining 1/2 cup of untoasted hazelnuts aside in a small bowl for decoration. Repeat the toasting process for all of the almonds. Add those to the hazelnuts in the bowl of the food processor and let cool for a few minutes. Process until the nuts are ground to a rough powder. Do not overprocess or they will turn into nut butter. Transfer the ground nuts to a medium bowl. Sift the confectioner's sugar over the top, add the salt, and stir to combine.
Using a stand mixer with the whip attachment (or a handheld mixer), beat the egg whites on medium speed until they hold soft peaks that droop gently when lifted, about 3 to 4 minutes (longer for a handheld mixer). On medium speed, add the granulated sugar to the whites in three equal additions, mixing for 30 seconds after each addition. When all of the sugar has been incorporated, increase the speed to high and beat for about 15 seconds longer. The meringue should be stiff and glossy. Remove the bowl from the mixer and sprinkle the nut mixture on top. With a rubber spatula, gently fold the nuts into the meringue, depositing the batter from the bottom on the bowl on top, rotating the bowl as you go.
Spread the mixture into rectangular shapes as marked on the parchment paper. Bake for 1-1/2 to 2 hours until the rectangles are firm to the touch. Turn off the oven and let them sit inside the warm oven for about 1 hour more to fully dry. Remove from the oven and let cool completely.
When the meringue layers are cool, make the ganache. Place the chocolate in a medium bowl. In a small saucepan, scald the cream over medium-high heat until bubbles start to form around the edge of the cream. Don't walk away or you risk it boiling over. Pour the hot cream over the chocolate and let it sit for 1 minute to soften the chips. Slowly whisk the chocolate and cream until the chocolate is completely melted and the mixture is smooth. Pour half of the mixture into a small, shallow bowl and set in the refrigerator covered for a half hour or so to thicken while making the buttercream. Leave the rest at room temperature so it remains a pourable consistency.
To make the espresso buttercream, make sure the butter is sitting out at room temperature first. Stir together the sugar and water in a small saucepan. Bring to a boil over high heat. While the sugar syrup is heating, wash the mixer bowl and whisk attachment. Beat the eggs and egg yolk together on medium speed for 3 to 4 minutes until pale in color. When the sugar syrup comes to a boil, cook without stirring, for 3 to 4 minutes until the temperature reaches 238°F on a candy thermometer. When the syrup is ready, remove from the heat. Turn the mixer speed down to low and slowly drizzle the hot syrup down the sides of the mixer bowl carefully so it doesn't hit the whip and splatter. When all of the syrup has been added, increase the speed to medium and whip for 6 to 8 minutes (again, longer with a handheld mixer) until the mixture is light and fluffy, and the bottom of the bowl is cool to the touch.
This is where things get scary. Turn the mixer speed down to low and add the room-temperature butter to the bowl a few chunks at a time. The mixture will break almost immediately into a disgusting, curdled mess. It will seem ruined. You will be cursing me. But keep mixing and it will come together again, trust me. It always does. Think to yourself, would Joanne Chang let me down? No, she would not. Increase the speed to medium and continue whipping for about 5 minutes until it turns smooth and silky. If it needs a few minutes more, go ahead. Add the espresso powder and salt, and whip until completely combined. If the buttercream should break again later on, I've always been able to get it to come back together again with enthusiastic mixing (sometimes in combination with a cold towel pressed against the bottom of the bowl).
For assembly, peel the cool dacquoise rectangles from the parchment paper. If any are misshapen, you can gently trim them down with a paring knife, but be careful not to shatter them as they're very fragile. Set one rectangle in the center of the chosen serving vessel. Remove the small bowl of ganache from the refrigerator and give it a brief stir to make sure it has thickened enough to mound without running. If not, refrigerate it for another half hour. If so, proceed to spooning a thick layer on top of the dacquoise up to about a half-inch from the edge. Use as much of the ganache as will reasonably fit to create a layer at least a half-inch thick. Press a second layer of dacquoise on top. Do the same with about 2/3 of the espresso buttercream (if it's starting to separate, give it a vigorous mixing before this step). Top the buttercream with the last dacquoise, placing it upside-down so the flat side is on top. Press lightly to adhere. Using a small spatula, spread the remaining buttercream into any gaps between the layers that are visible. Place the cake immediately into the refrigerator to chill for 1 hour.
Check that the ganache at room temperature is still pourable. If not, you can gently whisk it over simmering water just until fluid. Pour the ganache evenly over the cake, letting it drip down the sides. If the sides of your cake are visible, you can cover them with sliced almonds, but otherwise, any imperfections won't be seen. Decorate the top with reserved hazelnuts. Chill until ready to serve. Slice with a sharp knife.
Source: Adapted from Flour by Joanne Chang