Prep:Preheat oven to 350°F (175°C). Take two 8-inch (20-cm) cake pans and butter/oil the bottoms and sides. Line bottoms with a round of parchment paper, butter/oil the paper too. Dust with flour. Make batter:Sift flour, cocoa powder, baking powder, baking soda and salt into a medium bowl. In another bowl, whisk oil with sugar and vanilla. Beat in eggs one by one. Alternately beat in flour and milk, starting and ending with flour (flour-milk-flour-milk-flour). Scrape down the sides of the bowl. Whisk sweet cocoa powder into the hot coffee until it’s melted completely. Slowly whisk this into your batter and combine well. Divide the batter between the 2 prepared pans.
Bake for 30-35 minutes or until a cake tester inserted into the center comes out clean. If the cakes have risen too much in the center (and have that dome shape) gently press them down to flatten, using a damp tablecloth.
Allow cakes to cool in the pans for about 15 minutes. Invert the cakes onto wire racks, peel off the parchment and let cool completely.
Make the peanut butter frosting: In a large bowl and using an electric mixer, beat butter with peanut butter until fluffy. Gradually add powdered sugar, starting with 1 cup at a time. Mix thoroughly before adding more. Add the vanilla and beat on medium speed for a few minutes until the frosting is fluffy and light.
Assembly:Place one cake layer (flat side down) on a cake board or serving plate. Spread about 1/3 of the frosting (or a bit more) evenly over the top. Cover with the second layer, this time flat side up. Spread 1/3 of the frosting on top and the sides. Put the rest of the frosting in a piping bag. Chill cake and the bag with frosting for 15-30 minutes. Take cake out of the refrigerator. Frost the sides of cake again if you want a smooth (non-naked) finish. To decorate, pipe dollops on top of cake (to make a crown). Place a malt chocolate ball onto each dollop.
Refrigerate cake for it to fully set. Take it out about 30 minutes before serving for best flavor. Keep leftover cake in the refrigerator and eat within 2-3 days.