Very time consuming, but it's worth every minute! My method for making this cake - first toast coconut and walnuts, whip the egg whites, make the cake and while it's baking make the custard (I don't put it over an ice bath, I just let it cool in a bowl and stir it occasionally). While the cake and custard cool, make the frosting.
Italian Cream Cake
For the cake:
½ cup butter
½ cup solid vegetable shortening
1 ½ cups plus 1/3 cup granulated sugar
4 large eggs, separated
1 teaspoon vanilla extract
2 cups cake flour
1 teaspoon baking soda
½ cup buttermilk
½ cup toasted sweetened coconut flakes (toasted in oven at 350º or in skillet on stove over medium heat)
½ cup toasted walnuts (toasted in oven at 350º or in skillet on stove over medium heat)
For the pastry cream filling:
6 large egg yolks
½ cup granulated sugar
¼ cup all-purpose flour
2 tablespoons cornstarch
2 cups milk
1 ½ teaspoons vanilla extract
For the butter-cream cheese frosting:
¼ cup butter
¾ cup (6 ounces) cream cheese
2 cups confectioners’ sugar
1 teaspoon vanilla extract
1 teaspoon fresh lemon juice
1 ½ cups toasted sweetened grated coconut
Preheat the oven to 325º F.
To prepare the cakes, place the butter, shortening, and 1 ½ cups granulated sugar in the work bowl of an electric mixer. Beat at medium speed for about 30 seconds, until the mixture is fluffy. Turn down the speed to low and beat in the 4 egg yolks and vanilla, stopping to scrape down the sides of the mixing bowl. In a bowl, sift together the cake flour and baking soda and then add to the bowl of the mixer. Beat on slow speed for about 15 seconds, stopping once to scrape down the sides of the mixing bowl. Add the buttermilk, ½ cup toasted coconut, and ½ cup walnuts and beat for about 15 seconds longer, again scraping down the sides. Transfer the batter mixture to a clean mixing bowl. Clean and dry the work bowl of the mixer and add the egg whites and remaining 1/3 cup granulated sugar. Using the whisk attachment, beat on high speed for about 1 ½ minutes, until stiff peaks form. Fold the egg white mixture into the batter and mix well.
Spray two 9-inch cake pans with non-stick spray (or lightly butter the pans), line the bottoms with parchment paper, and evenly divide the cake batter between the pans. Transfer to the over and bake for about 30 minutes or until a toothpick inserted into the center of each cake comes out clean. Transfer the pans to a wire rack to cool. When cooled, run a paring knife around the inside rim of the cake pans to loosen the cakes, and invert them onto plates to release.
To prepare the pastry cream filling, place the egg yolks and granulated sugar in a mixing bowl and whisk with a wire whisk until pale yellow in color and ribbons form. In a separate bowl, sift together the flour and cornstarch and beat into the whisked egg yolk mixture. Pour the milk and vanilla into a small heavy-bottomed saucepan and bring to a simmer over medium heat. Slowly add the hot milk mixture to the egg yolk-flour mixture and whisk vigorously to temper. Pour the tempered mixture into the saucepan and continue cooking over low heat, whisking constantly, until almost boiling and thickened (if lumps form, whisk more vigorously until they disappear). Remove the pan from the heat and whisk for about 1 minute longer. Transfer to a clean bowl and set over an ice bath for about 5 minutes. Cover the surface of the pastry cream with plastic wrap and refrigerate until set, about 2 hours.
To prepare the frosting, place the butter and cream cheese in the work bowl of an electric mixer fitted with paddle attachment. Beat on medium speed for about 30 seconds, until fluffy. Add the confectioners’ sugar, vanilla, and lemon juice, and beat for about 30 seconds longer, until the mixture is completely incorporated.
Using a long, clean bread knife, cut the cakes in half horizontally (giving you four sections). Reserve one of the bottom-half sections. Top each of the remaining three sections with one-third of the pastry cream, using a spatula to evenly spread the pastry cream over the surface. Place the three cake sections on top of one another, with the pastry cream facing up. Place the reserved cake section upside-down on the top of the other three sections, so the bottom side faces up.
Using a metal spatula or a pallet knife, evenly cover the top and sides of the cake with the frosting. Once the cake is frosted, lift it up, holding the cake from the bottom, and press the coconut flakes into the sides of the cake. Place the cake on a serving platter and top with the remaining coconut, gently pressing it into the frosting. Serves 10-12