1 cup Irish Stout Beer
10 Tablespoons (1 stick plus 2 tablespoons) Unsalted Butter
1/4 cup Dark Brown Sugar
1 3/4 cups Superfine/Caster Sugar
3/4 cup Unsweetened Cocoa Powder
3/4 cup Sour Cream
2 Large Eggs
1 Tablespoon Vanilla
2 cups Flour
2 ½ teaspoons Baking Soda
6 Egg Whites
1 1/2 cups Light Brown Sugar
1 pound Salted Butter (4 sticks - 32 Tablespoons), at room temperature
2/3 cup Malted Milk Powder
2 teaspoons Vanilla
5oz-12oz Box Whoppers Malted Milk Balls Candy
Preheat the oven to 350.
FOR THE CAKE:
In a saucepan, combine Irish Stout Beer and butter. Place saucepan over medium-low heat until butter melts.
Whisk in dark brown sugar into butter mixture and stir until it dissolves.
Cut the heat, whisk in caster sugar and cocoa powder.
Whisk until smooth.
In a small bowl, whisk together sour cream, eggs and vanilla.
In another bowl, whisk together flour and baking soda.
Whisk sour cream mixture into the melted butter mixture.
Once the sour cream mixture is fully incorporated into the butter mixture, whisk in the flour mixture.
Mix until batter is smooth.
Grease and flour two 9" cake rounds, or line with baking parchment.
Divide cake batter between pans.
Bake at 350 degrees for about 30-35 minutes, until a toothpick comes out clean on doneness check.
Let cakes rest 5 minutes, then turn out cakes to cool on a cooling rack.
FOR THE BUTTERCREAM:
Fill a medium saucepan with 2-3 inches of water.
Bring water to a boil over high heat. Once boiling, reduce to a simmer.
Combine egg whites (reserving yolks for another use) and light brown sugar in the metal mixing bowl of a stand mixer (or if not using a stand mixer another metal bowl) and place over the simmering water.
Whisk while heating until the sugar is dissolved and mixture temperature reaches 180 degrees (measure temperature with a candy thermometer, or other kitchen thermometer).
Using a whisk attachment on a stand mixer (or with a hand mixer) whisk egg whites and sugar on high until they double in volume. Mixture will be thick and shiny.
Reduce speed of the mixture to medium and begin to add butter about 1/2 tablespoon at a time, until all the butter is incorporated. It is important that butter be room temperature and that you allow it to fulling incorporated between each mix in.
Once all the butter is incorporated, slowly beat in the malted milk powder.
Beat in vanilla.
NOTE: If mixture looks broken, increase speed to high and whisk until smooth. If the mixture looks too lumpy, the butter is too cold, applying heat to the bowl while mixing will help smooth it out. You can apply heat with a torch or by holding a hot pot against the side of the bowl while it mixes. If the mixture looks too runny, then the butter is melted. You can remedy that by holding an ice pack against the bowl while it mixes. You will see the frosting tighten up. This may seem fussy, but the texture of this cream filling is worth it!
Cut one of the cake halves to flatten the top. This will be for the bottom cake layer.
Pulse malted milk balls in a blender to break up (reserving some whole for decorating the cake if you wish)
Cover the top of the bottom layer cake with buttercream.
Sprinkle buttercream with broken up malted milk balls.
Place second cake layer over buttercream.
Frost entire cake with buttercream and decorate with malted milk balls as desired.