• Chocolate Cake Layers
• Preheat oven to 350 F / 175 C. Grease and line four, eight-inch cake pans.
• Sift or whisk together the dry ingredients (flour, sugar, cocoa powder, baking powder, baking soda and salt) into a large bowl.
• Pour in the warm water, buttermilk, oil, eggs, and vanilla into a separate bowl and whisk together until fully incorporated.
• Mix the wet ingredients into the dry ingredients just until they're incorporated into the batter. Do not over-mix!
• Divide the batter evenly between the prepared cake pans and bake for about 23-26 minutes or until a toothpick comes out with a few moist crumbs.
• Remove the cake layers from the oven and let them cool in the pans for about 10 minutes. Gently run an offset spatula around the rim of the cake pans to loosen them, then flip them into wire racks to finish cooling.
• Once cooled, use a serrated knife to level the top of each cake layer. If you are making these cake layers in advance, wrap and freeze them at this point. These can be made up to a month in advance.

Caramel Drizzle

• Make the caramel drizzle while the cake layers bake and cool. This can be made up to a month in advance.
• Place a medium saucepan over medium to medium-high heat.
• Once the pan has warmed up, pour in 1 cup sugar gradually, adding 1/4 cup at a time. Wait until the sugar is mostly dissolved, then add in the next bit of sugar.
• As the sugar melts it will gradually deepen in color.
• Stir occasionally until the sugar is fully dissolved and has become an amber color, then turn off the heat.
• Slowly mix in 6 Tbsp of butter (2 Tbsp at a time), then stir in 1/4 cup of heavy cream and 1/4 tsp salt. The mixture will be thin but will thicken as it cools.
• Pour into a separate container, then place in the fridge to cool and/or store. When you're ready to use it, heat the caramel in the microwave in short 10 second intervals until it's a more workable consistency.

Chocolate Ganache Drip

• Next, make the chocolate ganache drip. Place 1/2 cup semi-sweet chocolate chips in a heatproof bowl and set aside.
• Heat 1/3 cup of heavy cream in a heatproof bowl in the microwave for 45 seconds to 1 minute, until it's steaming and just starting to bubble. If you don’t have a microwave or prefer to use the stove top, you can heat the cream over a medium heat in a pan until it begins to simmer. Remove from heat.
• Gently pour the heavy cream over the chocolate, making sure it's fully covered with cream. Allow the mixture to sit for 1-2 minutes.
• Stir slowly until the cream and chocolate are fully combined and the mixture is smooth.
• Set aside to cool for about 10 minutes, until the mixture is just slightly warm to the touch. Cover with plastic wrap or pour into a plastic squirt bottle and set aside.

Chocolate Buttercream Frosting

• Then make the chocolate buttercream frosting. Beat the butter on a medium speed for 30 seconds with a paddle attachment until smooth. 
• Add in the sifted cocoa powder, vanilla extract, and salt. Mix on low until the ingredients are fully incorporated.
• Slowly mix in the powdered sugar. Halfway through, add in the heavy cream to make the frosting easier to mix.
• Mix in the cooled, melted milk chocolate on a low speed until the ingredients are fully incorporated and the desired consistency is reached. Cover with plastic wrap to prevent crusting and set aside.

Fluffy Chocolate Cake Filling

• Make the fluffy chocolate cake filling last. It's a bit more time-sensitive and it's best to make it right before you assemble the cake. It can sit out at room temperature for about 3 hours, but it begins to lose its shape if it sits longer than that.
• Place the egg whites, sugar, and cream of tartar in a heatproof (preferably metal) bowl. Set the bowl over a saucepan filled with an inch or two of simmering water. Make sure the metal bowl does not touch the water!! If it does, it can cook /scramble the egg whites.
• Whisk constantly for about 4 minutes, until sugar is fully dissolved and has become thinner and lighter in color. The mixture will feel thick and tacky at first but will become thinner and start to look a bit frothy on top. I like to do the finger test to see if the meringue is ready, but you can also use a thermometer. To test with your fingers, dip a tiny bit of your pointer finger (it’s very hot, be careful) and rub the mixture between your thumb and finger. It should feel smooth, and you shouldn’t be able to feel any sugar granules. If you use a thermometer, the temperature should be 160 F / 70 C.
• Remove from heat and add the vanilla extract. Use a handheld or stand mixer fitted with a whisk attachment to beat on high speed for about 5 minutes, until stiff glossy peaks form.
• Mix in the butter, cocoa powder, and pinch of salt on a medium speed. Scrape around the side and bottom of the bowl as needed with a rubber spatula.

Assembling This Milky Way Cake

• Stack and frost cake layers on a greaseproof cake board, using a dab of chocolate buttercream to help stick the first cake layer to the board.
• As you assemble the cake, pipe a ring of chocolate buttercream around each cake layer. Spread about 1/3 of the fluffy chocolate cake filling inside the buttercream ring. Top with a generous drizzle of caramel.
• Repeat with the remaining cake layers. Smooth any overhanging buttercream around the cake with a large offset spatula. Then freeze the cake for about 10 minutes in the freezer or 30 minutes in the fridge. This will help the buttercream between the cake layers firm up and make the cake easier to frost.
• Carefully cover the cake with a thick, even layer of chocolate buttercream and smooth using a bench scraper. Chill the cake one more time in the fridge or freezer until the buttercream is firm to the touch.
• Heat up the caramel and chocolate ganache in the microwave for short 5-10 second intervals until they're a good consistency to add drips around the cake.
• Remove the cake from the fridge and add a test drip using both the chocolate ganache and the caramel to the back of the cake. Adjust the temperature of the caramel and the ganache as needed (hotter for longer drips, or let it cool more for shorter/thicker drips). Add chocolate and caramel drips around the cake.
• Decorate the top of the cake with a ring of sliced Milky Way bars and enjoy!