1–1/2 cups (340 gm) unsalted butter, at room temperature
3 cups (375 gm) powdered sugar
½ cup (55 gm) chocolate malt powder (like chocolate ovaltine)
2 teaspoons vanilla extract
¼ teaspoon salt
6 tablespoons (90 gm) heavy whipping cream
6 ounces (190 gm) dark chocolate (I use 70%), chopped, melted, and cooled
To prepare the cake:
Preheat oven to 350 degrees. Spray 3 (8″) round cake pans with baking spray and line the bottoms with parchment rounds.
In the bowl of a stand mixer, combine all of the dry ingredients and stir until combined. In a separate bowl, loosely combine all of the wet ingredients and these to the bowl of the dry ingredients. Mix on medium speed for just shy of 2 minutes, scraping the bowl (and bottom of bowl!) twice throughout.
Pour equal amounts of batter in to all 3 pans. Carefully place in the oven and bake for about 30 minutes, or until center is just barely set and toothpick comes out of cake almost clean. Allow to cool in the pans and on a cooling rack for 20 minutes and then remove from pans to continue the cooling process. Allow to cool completely prior to frosting. (see notes)
To prepare the brownie filling:
In a medium bowl combine the first 6 ingredients on medium speed just until combined. Add water a teaspoon at a time until it becomes a thick, brownie batter consistency. Set aside until ready to use.
To prepare the frosting:
In the bowl of a stand mixer, combine the butter and sugar and beat on low speed for 1 minute until combined. Add the malt powder, vanilla, and salt and stir on low until combined. Add the melted chocolate, increase the speed to medium, and whip for 2 minutes. Scrape the sides of the bowl and add the whipping cream. Beat on medium-high speed for one minute.
To assemble the cake:
Use a serrated knife to cut the domes off each cake. Put some of the frosting into a piping bag or plastic bag with the end cut off of it. Place one layer on a cake board or serving platter and pipe a ½” dam or frosting around the perimeter of the cake. Fill it just under the top of the frosting with brownie batter filling and top with an additional layer of cake. Repeat this process once more. Coat the stacked cake with a thin layer of frosting and place in the fridge to set up. Continue frosting as desired and serve!
I find this cake is easiet to work with when the layers are partially frozen. Wrap the baked and cooled layers in plastic wrap and place in the freezer overnight or for a few hours. Thaw out for 15 minutes prior to using.