Preheat the oven to 350°F / 175°C. Line three 8-inch cake pans with parchment paper rounds and spray with non-stick baking spray.
In a large bowl, whisk together 3 cups flour, 2 1/2 cups granulated sugar, 1 tsp salt, 1 1/2 tsp baking powder, and 1 tsp baking soda. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or using a hand mixer, beat 1 cup butter on medium speed until smooth and creamy.
Add the dry ingredients to the butter and mix on low speed until the mixture resembles coarse sand.
In a separate bowl, whisk together 4 eggs, 1 cup hot water, 1 cup buttermilk, and 1 cup cocoa powder until smooth.
Slowly add the wet ingredients to the dry ingredients, mixing on low speed until just combined. Scrape down the sides of the bowl as needed.
Divide the batter evenly between the prepared pans. I recommend using a kitchen scale to ensure even layers.
Bake for 33-35 minutes or until a toothpick inserted in the center comes out with a few moist crumbs.
Let the cakes cool in the pans for 10 minutes, then run an offset spatula around the edges and flip onto a wire rack to cool completely.
Chocolate Simple Syrup
While the cakes are baking, combine 1 cup of sugar, 1 cup of water, and 2 Tbsp of cocoa powder in a small saucepan.
Bring to a boil over medium heat, stirring occasionally, then reduce heat and simmer for 5 minutes.
Remove from heat and let cool completely before using.
Milk Chocolate Ganache Filling
Place 2 cups or 340g of milk chocolate chips in a heatproof bowl.
Heat 1 cup of heavy cream in a small saucepan until it just begins to simmer (do not boil).
Pour the hot cream over the chocolate chips and let sit for 2 minutes.
Whisk slowly until smooth and fully combined.
Allow the ganache to cool at room temperature, stirring occasionally, until it reaches a spreadable consistency (about 1 hour). If needed, you can speed up this process by refrigerating for 20-30 minutes, stirring every 10 minutes.
Once it's reached room temperature, place it in a large piping bag fitted with a round piping tip and set aside.
Whipped Chocolate Buttercream
Melt 1/2 cup milk chocolate chips in the microwave in 30-second intervals, stirring between each, until smooth. Set aside to cool slightly.
In a large bowl or stand mixer fitted with the paddle attachment, beat 1 cup of butter on medium speed for 2 minutes until light and fluffy.
Mix in 1/2 tsp salt and the melted chocolate, beating until fully incorporated.
Gradually add 3 1/2 cups powdered sugar, mixing on low speed. Add 1/4 cup heavy cream halfway through to help combine.
Add 1 Tbsp egg whites and increase the speed to medium-high. Beat for 3-4 minutes until very light and fluffy.
If the frosting is too thick, add more heavy cream, 1 Tbsp at a time. If too thin, add more powdered sugar. 1/4 cup at a time. Place in a large piping bag fitted with a round piping tip and set aside.
Assembling This Cake
I recommend assembling this naked chocolate cake the same day you plan to eat it if possible. The assembly process is pretty simple and only takes about 10 minutes.
Level the cake layers with a serrated knife if needed. Then place the first layer on a cake board or serving plate. Brush generously with the chocolate simple syrup using a thick, sterile brush.
Pipe dollops of whipped chocolate buttercream and chocolate ganache onto the cake layer. Top with a second cake layer and repeat.
Place the top cake layer upside down. Use the remaining buttercream or ganache to pipe swirls on top of the cake using a Wilton 1M tip. Garnish with chocolate sprinkles then enjoy!
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Notes
Both the chocolate simple syrup and the chocolate ganache filling need time to chill! I highly recommend making them the night before. The ganache can sit out at room temperature overnight and will be ready to use the following day.
Tips for Making the Best Naked Chocolate Cake
Properly measure your flour (spoon it into the cup measure, then level) or use a kitchen scale for accuracy.
Make sure all refrigerated ingredients are at room temperature before mixing for the best texture.
Don't overmix the batter once the flour is added to prevent a dense cake.
The chocolate simple syrup adds moisture and intensifies the chocolate flavor.
For extra flavor, add 1 tsp of espresso powder to the hot water before mixing with cocoa.
If your whipped buttercream isn't as thick as you'd like, place the bowl in the freezer for about 5 minutes, then beat on high again for about 1 minute.
Making This Naked Chocolate Cake in Advance & Storage Tips
The cake layers can be made ahead and frozen for up to a month if wrapped well in plastic wrap and stored in an airtight container.Buttercream can be stored in an airtight container in the fridge for up to two weeks or frozen for up to three months.The chocolate simple syrup can be stored in the refrigerator for up to a month.For best taste and texture, assemble the cake the day you plan to serve it.