12-layer Chocolate Cake Recipe

Prepare

Preheat the oven to 350°F (175°C). Grease and line twelve 6-inch round cake pans with parchment or, if you have fewer pans, plan to bake in batches (batter will be portioned later). Bring eggs and milk to room temperature; measure ingredients.

Dry ingredients

In a very large mixing bowl, sift or whisk together the flour (5 cups), cocoa powder (1 cup), baking powder (3 tsp), baking soda (3 tsp), salt (2 tsp), and granulated sugar (3.5 cups) until evenly combined. Whisk for about 30 seconds to aerate.

Wet ingredients

In a second large bowl, whisk the eggs (6) lightly, then add the whole milk (3 cups), vegetable oil (1.5 cups), and vanilla extract (3 tbsp). Whisk until homogenous.

Combine batter

Make a well in the dry ingredients and slowly pour in the wet mixture, stirring with a sturdy spatula or mixer on low. Add the hot water or coffee (2 cups) gradually — the batter will be thin; this is expected and gives a moist crumb. Mix just until fully combined, scraping the bowl sides. Do not overmix.

Portion & bake

If using twelve 6-inch pans: divide batter evenly among the pans (use a scale or measure by volume — about equal amounts). If using larger pans, bake in batches and trim layers later to yield twelve thin layers. Bake 12 layers at 350°F for 12–16 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Rotate pans halfway through baking for even color. If baking in larger pans, bake 20–28 minutes and cool before slicing into layers.

Cool

Allow the cakes to cool in pans for 10 minutes, then invert onto racks and remove parchment. Cool completely (at least 1 hour) before assembling so frosting doesn't melt.

Make simple syrup by heating 1 cup sugar and 1 cup water until sugar dissolves; cool slightly. Stir in optional 1/4 cup dark rum or coffee liqueur if using. Keep warm for brushing.

Lightly brush each cake layer with a thin coating of syrup to add moisture and flavor. Use about 1–2 tablespoons syrup per 6-inch layer; do not soak until soggy.

Prepare butter

In a large stand mixer bowl fitted with the paddle attachment, beat the room-temperature unsalted butter (4 cups) on medium speed for 2–3 minutes until creamy and pale.

Add dry elements

With the mixer on low, sift in confectioners' sugar (12 cups) and cocoa powder (1.5 cups) in three additions to avoid dust clouds. After each addition, mix briefly to incorporate then increase speed to medium-high for 20–30 seconds to aerate. Scrape down the bowl as needed.

Finish buttercream

Add heavy cream (1.5 cups) in 3–4 additions while mixing on medium. Add vanilla (3 tsp) and salt (1 tsp). Beat on medium-high for 2–3 minutes until light, fluffy, and spreadable. Adjust consistency: if too stiff, add additional cream, 1 tablespoon at a time; if too loose, add a little sifted powdered sugar (1–2 tbsp at a time).

Level each cooled cake layer with a serrated knife or cake leveler so layers stack evenly. Place the first layer on a cake board or serving plate and secure with a small dab of buttercream.

If using, lightly brush the layer with simple syrup. Spread a thin, even layer of chocolate buttercream (about 1/2 to 3/4 cup per layer depending on thickness desired) over the layer using an offset spatula.

Repeat stacking and frosting for all twelve layers. Aim for even pressure and alignment so the cake remains straight. If layers are thin, use a small amount of frosting between layers to prevent sliding.

Once all layers are stacked, apply a thin crumb coat of buttercream over the entire cake to lock in crumbs. Chill the cake in the refrigerator for 20–30 minutes until the crumb coat is set.

Apply a final thicker coat of buttercream, smoothing with an offset spatula or bench scraper for clean sides and top. If desired, pipe decorative borders or rosettes using any remaining buttercream.

Garnish the top and/or sides with chocolate shavings or a dusting of cocoa powder (about 1/2 cup of shavings). Refrigerate the assembled cake for 30 minutes to set the frosting before slicing.

Bring chilled cake to room temperature for 30–60 minutes before serving for best texture and flavor. Slice with a hot, clean knife (dip in hot water and wipe between cuts) to get neat slices.

Store any leftover cake covered in the refrigerator for up to 5 days. For longer storage, slice and freeze layers or portions wrapped tightly; thaw overnight in the refrigerator before serving.