Let’s embark on creating this exquisite Ferrero Rocher Cake! First, prepare the oven and pans. Preheat your oven to 350°F (175°C). Line the bottoms of two 8-inch round cake pans with parchment paper circles and spray the sides (and parchment) well with non-stick spray. Set aside.

Prepare the chocolate component. Melt the bittersweet chocolate chips in a microwave-safe bowl at 50% power in 30-second intervals, stirring well after each, until smooth. Alternatively, use a double boiler. While the chocolate is still warm, add the Nutella and whisk until the mixture is completely smooth and glossy. Set aside to cool slightly but remain fluid.

Prepare the hazelnut flour mixture. Place the whole hazelnuts, confectioner’s sugar, cocoa powder, all-purpose flour (if using), baking powder, and salt into the bowl of a food processor. Pulse repeatedly until the mixture becomes a fine, sandy flour consistency. Be careful not to over-process, or you might end up with hazelnut butter. Set this hazelnut flour mixture aside.

In the large bowl of your stand mixer fitted with the paddle attachment (or using a handheld mixer), beat the softened butter and granulated sugar on medium-high speed until very light and fluffy, about 3-5 minutes. Add the 2 tablespoons of Frangelico (or substitute) and the 7 egg yolks (ensure no whites got in!). Mix on medium speed until well combined, scraping the bowl as needed.

Gently fold the cooled chocolate-Nutella mixture into the butter-yolk mixture using a large spatula until just combined. Then, add the prepared hazelnut flour mixture and fold it in gently until just incorporated. Do not overmix. Transfer this very thick batter to a separate large bowl. Thoroughly clean and dry your mixer bowl and whisk attachment – any grease will prevent the egg whites from whipping properly.

Place the 7 egg whites into the clean, dry mixer bowl. Using the whisk attachment, beat the egg whites on medium-high speed until they form stiff, glossy peaks. Stiff peaks mean that when you lift the whisk, the peak holds its shape and doesn’t flop over.

Now for the critical folding step: Gently add about one-third of the whipped egg whites into the thick chocolate-hazelnut batter. Fold them in using your large spatula to lighten the batter slightly. Add the remaining whipped egg whites in two more additions, folding very gently but thoroughly after each addition. Scrape from the bottom of the bowl, bringing batter up and over the whites, rotating the bowl. Fold only until no large streaks of egg white remain. Be extremely careful not to deflate the egg whites, as they provide the cake’s primary lift.

Carefully divide the finished airy batter evenly between the two prepared cake pans. Smooth the tops very gently. Bake in the preheated oven for 35-40 minutes, or until a wooden toothpick inserted into the center comes out clean. The cakes might rise significantly and then settle slightly upon cooling.

Let the cakes cool completely in their pans on wire racks. The recipe notes they are fragile, so handle with care. Once completely cool, carefully run a thin knife or offset spatula around the edges and invert the cakes. Peel off the parchment. Now, using a long, sharp serrated knife, very carefully split each cooled cake layer horizontally in half, creating four thin, fragile cake layers in total.

Prepare the Nutella Frosting. In a large bowl (or stand mixer bowl with paddle), beat the softened butter and Nutella together on medium-high speed for 5-6 minutes until very light, pale, and fluffy. Add the optional salt. Gradually add the sifted confectioner’s sugar, about half a cup at a time, mixing on low speed until incorporated, then increasing speed briefly. Once all sugar is added, beat on medium-high for another 3-4 minutes until the frosting is thick, smooth, and very fluffy.

Assemble the cake. Place one fragile cake layer onto your serving plate or cake stand. Using a pastry brush, lightly soak the layer with some of the 1/2 cup of Frangelico (or substitute). Spread a layer of Nutella buttercream over the soaked cake (about 1/4 to 1/3 of the total frosting, reserving enough for the outside). Sprinkle a generous layer of crushed wafer cookies evenly over the frosting.

Carefully place the second cake layer on top. Repeat the process: soak with liqueur, spread with buttercream, sprinkle with crushed wafer cookies. Repeat again with the third cake layer: soak, buttercream, crushed wafers. Place the fourth and final cake layer on top and soak it lightly with liqueur.

Apply a thin crumb coat of the Nutella buttercream all over the cake (top and sides) to trap any crumbs. Chill the cake for 20-30 minutes to firm up the crumb coat. Use the remaining Nutella buttercream to frost the top and sides of the cake smoothly (or create textures if desired) using your offset spatula.

Garnish the top of the cake with whole Ferrero Rocher candies and whole or chopped toasted hazelnuts. You can arrange them decoratively around the edge or in the center. Refrigerate the finished cake for at least 1-2 hours to allow the frosting and layers to set firmly before slicing. Remember to let it sit out for about an hour before serving for the best texture.