Layered espresso spiked cake with brown butter buttercream and chopped toasted pecans and hazelnuts
Yield: 6-inch cake
Preheat oven to 350 degrees F. Grease three 6-inch round cake pans and line with parchment paper. Set aside.
In a large bowl, whisk together flour, almond flour, baking powder, cinnamon, and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, cream butter. Add sugar and mix until smooth and fluffy. Scrape down bowl as needed to ensure thorough mixing.
On medium speed, add eggs one at a time, making sure each egg is incorporated before adding the next. Scrape down bowl as need. **Make sure eggs are room temperature. Otherwise, batter may curdle. If batter starts to curdle, mix in 2-3 Tablespoons of dry flour mixture until smooth.
Dissolve espresso powder into espresso liquid. Set aside.
On low speed, add dry flour mixture in three additions, alternating with espresso mixture. Start and end with flour mixture. Scrape down bowl as needed. Mix until just combined and there are no longer any dry streaks of flour.
Evenly divide cake batter among prepared cake pans. Level batter using a mini offset spatula, or the back of a spoon. Tap bottom of cake pan against hard surface to push out air bubbles.
Bake for 23-25 minutes until toothpick inserted in center of cake comes out clean. Let cool in pan for 5 minutes before running knife or offset spatula along sides of cake. Unmold cake and allow to cool to room temperature on wire rack.
In a heavy bottomed sauce pan, melt butter over medium heat. Once the butter has melted, continue to cook. Swirl pan occasionally to ensure even heating. Mixture will bubble and foam as it cooks. The bubbling will be vigorous at the beginning but it will subside. Continue to cook until butter smells nutty. The mild solids in the butter will turn rich brown in color. Remove from heat and pour into a heat-safe bowl. Be sure to scrape out as much of the browned milk solids bits.
Allow brown butter to cool to room temperature. Cover and keep chilled in the fridge until solid. Brown butter needs to be completely cooled before mixing into buttercream.
Allow solid brown butter to soften at room temperature. Transfer to the bowl of stand mixer fitted with a paddle attachment (or use an electric hand mixer). Beat until smooth. Add confectioners sugar, instant espresso powder, salt, and milk. Mix until buttercream is soft and fluffy. Scrape down bowl as needed to ensure thorough mixing.
Preheat oven to 350 degrees F. Line two baking sheet with parchment paper. Spread pecans in an even layer on one tray and hazelnuts on the other tray. Bake for 10-12 minutes until nuts are fragrant. Pecans may cook faster. Hazelnuts are done once skins start to peel off.
Midway through baking, stir nuts around to ensure thorough toasting. Be mindful, nuts can go from toasted to brunt very fast!
Allow toasted pecans to cool. To remove hazelnut skins, place hot hazelnuts in a kitchen towel. Rub hazelnuts together until skins fall off. Do not worry if all the skins do not come off.
Allow nuts to cool to room temperature before assembly. Finely chop about 2 tablespoons pecans and 2 tablespoon hazelnuts. Set aside. Roughly chop remaining nuts.
If necessary, use a serrated knife to level off cake layers once cake has completely cooled.
Place one cake layer on cake board, serving plate, or cake turntable. Spread a layer of buttercream over cake. Sprinkle 1 1/2 tablespoon of finely chopped nuts over buttercream. Top with second cake layer and repeat adding buttercream and nuts.
Add third cake layer and top with buttercream. Spread a thin layer of buttercream around the exterior of assembled cake to seal in crumbs. Chill in the fridge for 10-15 minutes to set up.
Add a final coat of buttercream around the exterior of cake. Keep cake chilled in the fridge until ready to serve.
Allow cake to sit at room temperature for 30 minutes before serving. If desired, add remaining buttercream to a pipping bag fitted with a star tip. Decorate the top of cake with a piped border. Before slicing and serving, garnish cake with roughly chopped toasted nuts. Garnish each cake slice with additional chopped nuts.