How to Make It
Preheat the oven to 325°. Butter and flour three 8-inch cake pans and line the bottoms with parchment paper. In a large bowl, whisk the flours with the malt powder, baking powder, baking soda, salt and nutmeg.
In the bowl of a standing electric mixer fitted with a paddle, beat the butter with the shortening until creamy. Add the sugar and vanilla and beat at medium speed until fluffy, about 3 minutes. Beat in the dry ingredients in 3 batches at low speed, alternating with the ice water, occasionally scraping down the side of the bowl.
In a clean bowl, beat the egg whites at medium-high speed until soft peaks form. Fold the egg whites into the batter. Divide the batter between the pans, spreading it evenly, and bake the cakes for 40 to 45 minutes until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 20 minutes, then invert them onto a rack and let cool completely. Peel off the parchment.
Place the chocolate in a large bowl. In a small saucepan, bring the cream to a boil, then remove from heat. Add the corn syrup; immediately pour the mixture over the chocolate. Let stand for 2 to 3 minutes, until the chocolate has melted, then whisk until smooth. Let cool to room temperature.
Transfer the mixture to the bowl of a standing electric mixer fitted with a wire whisk. Gradually beat in the butter at medium speed, a few chunks at a time, and beat until thoroughly incorporated between additions. The frosting should be smooth and silky. Refrigerate the frosting just until it is thick enough to hold its shape, 10 to 15 minutes.
Place one cake layer on a serving platter and spread 1 1/4 cups of the frosting over the top in an even layer. Repeat to form 2 more layers. Spread a thin layer of frosting over the side of the cake and refrigerate briefly until firm. Frost the side with the remaining frosting. Garnish the cake with malted-milk balls and refrigerate briefly to firm up the frosting before serving.