In this White Chocolate Macadamia Cake spongy cake layers are filled with fluffy coconut Swiss meringue buttercream and encapsulated in a rich white chocolate ganache glaze
Preheat oven to 325°F. Generously grease and flour two 9-inch round cake pans. Line the bottoms with parchment paper circles.
In the bowl of your mixer, whip the butter on medium speed until fluffy (about 2 minutes). Gradually add the sugar and whip to incorporate. Occasionally scrape down sides of the bowl. Add eggs one at a time, scrape down bottom and sides of the bowl after each addition. Mixture may look curdled at first, but will smooth out soon. Add sour cream and vanilla and combine well.
Whisk egg whites and sugar together until combined. Set the bowl over simmering water in a double-boiler and whisk gently until the sugar is dissolved and the egg whites are hot (160°F).
Transfer egg syrup to a shallow bowl or cake pan and refrigerate until cooled (45-60°F).
In the meantime whip the softened butter until fluffy and light in colour. Pour in 1/2 of the cooled egg syrup and whip 2 minutes until fully incorporated. Then add the rest of the egg syrup, coconut extract, and salt. Continue whipping until incorporated and the buttercream is light and fluffy.
Makes a good 3 cups of buttercream. Use 1/2 as filling between cake layers, and the rest for frosting the top and sides of the cake.
Very roughly chop the toasted macadamia nuts.
Cut both cake layers in half horizontally so you end up with 4 layers. Place the first one onto a cake board or plate and evenly spread 1/2 cup of buttercream onto the cake layer. Sprinkle 1/3 of the chopped nuts over the buttercream. Then top with the second cake layer and repeat for the next two layers.
Once the four cake layers are assembled and filled, cover the top and the sides with the remaining buttercream. Chill the cake in the fridge until fully set and firm to the touch.
For the ganache glaze, chop white chocolate into small pieces and place in a bowl. Set aside. Bring heavy cream to a simmer, remove from heat and pour over white chocolate pieces. Cover with a plate and let the mixture sit for 5 minutes, then carefully stir until a smooth ganache forms.*
Let ganache cool until it is no longer warm to the touch (84°F/28°C) but still is pourable and hasn’t hardened.
Place a wire rack on a baking sheet. Put the cake on the rack. This way excess ganache will drip onto the baking sheet and can be reused. Pour the white chocolate ganache glaze onto the chilled cake and let it also run down to cover the sides. Use an angled spatula to smooth out the top
Let the cake sit for just a minute and scrape excess drip from the bottom edge, then move the cake (and rack) to the fridge to let it firm up. Store the cake in the fridge until 1/2 to 1 hour before serving. The ganache will be easier to cut with a hot knife.
*if the white chocolate doesn't melt fully, you can place the ganache over a double-boiler and heat gently while stirring until the chocolate is fully melted and ganache is smooth