For the Walnut Cake:
- 2 cups Fisher Brand Walnuts halves and pieces
- 6 large eggs room temp
- 1 cup granulated sugar
- 1 cup all-purpose flour
- 1/2 tsp baking powder
For the Russian Buttercream:
- 3/4 cup sweetened condensed milk 2/3 of a 14 oz can
- 2 large egg yolks
- 1 Tbsp water
- 1/2 tsp vanilla extract
- 3 sticks 1 1/2 cups unsalted butter, softened at room temperature
For the Simple Cake Syrup (stir these ingredients together):
- 1/4 cup granulated sugar
- 1 cup warm water
- 3 Tbsp rum – I used Bacardi golden rum*
For the Chocolate Sauce/ Ganache:
- 4 oz or 1/4 lb by weight, or 2/3 cup by dry measuring cup semisweet chocolate chips
- 1/2 cup heavy whipping cream
How to Make the Royal Walnut Cake:
Toast 2 cups walnuts on a dry skillet over medium/high heat until fragrant and golden (5 minutes), tossing often. Cool to room temperature then finely chop or pulse in food processor.
Preheat oven to 350˚F. Line the bottoms of two 9″ baking pans with parchment paper (do not grease the pan). In the bowl of a stand mixer fitted with whisk attachment, beat eggs for 1 minute until foam. With mixer on, add 1 cup sugar in a steady stream then beat on high speed 8 minutes. Batter will be fluffy and a thick ribbon will form when you lift up batter.
Whisk together 1 cup flour and 1/2 tsp baking powder and sift it into the egg mixture in 3 increments. Gently fold in 1/4 of your cooled chopped nuts and divide batter evenly between 2 prepared pans. Bake right away in fully preheated oven at 350˚F for 23-28 min(I find it’s perfect at 25 min). Let rest in the pans 5 min then run a thin spatula or knife around the edges of pan to loosen cake and transfer cakes to wire rack to cool completely to room temp.
How to Make Russian Buttercream:
In a small sauce pan, off the heat, whisk together 2 egg yolks, 3/4 cup condensed milk, 1 Tbsp water, and 1/2 tsp vanilla until smooth.
Place over low heat. Continue stirring frequently and stir constantly as it starts to thicken – DO NOT BOIL. When it’s ready, it will be the consistency of uncooked sweetened condensed milk. Total time on the stove: 5-7 minutes. Remove mixture from heat and let custard cool completely to room temp. It will thicken more as it cools.
Beat softened butter in a mixer with whisk attachment for 5 minutes on high speed until white and fluffy, scraping down the bowl as needed. Add room temp custard mixture 1 heaping Tablespoon at a time, beating on high speed for a few seconds with each addition. Once all of the custard is incorporated, scrape down the bowl and beat another 2 minutes on high speed. Reserve 1 cup of cream and set aside (you’ll use this to coat the top and sides of cake). Fold in 1/4 of your toasted cooled nuts into remaining big batch of cream.
Assembling the Walnut Cake:
Line the edges of a cake platter with strips of parchment paper (this will make cleanup easier). Place first cake layer on the platter and spoon half of the syrup evenly over the top. Top with all of your walnut buttercream and spread evenly. Add the next cake layer and spoon the remaining syrup over the top. Coat the sides and top of the cake evenly with remaining 1 cup of buttercream.
Apply the remaining finely chopped walnuts to the sides of the cake only, scooping it on with your hand and gently pressing for the nuts to adhere to the frosting. Now make your ganache (see below). Once ganache has rested 5-10 minutes, spread it evenly over the top of the cake, allowing some of it to drip down the sides of the cake. Let cake rest until ganache is set (you can refrigerate 30 min if desired).
How to Make Chocolate Ganache:
Place 1/4 lb of chocolate chips in a heat-proof bowl. Pour 1/2 cup heavy cream into a small saucepan and bring to a simmer. When it’s just at a uniform simmer, pour over the chocolate chips ensuring chocolate is fully submerged in cream. Cover bowl with lid and let sit at room temp 15 min then whisk until a silky chocolate sauce forms. Let ganache rest 5-10 min to thicken slightly but still be loose enough to pour over the cake and drip down the sides.
*if you don’t want to use rum, add a splash of vanilla or 2 Tbsp fresh lemon juice, or add it to taste