Yield: One 4-layer, 8-inch cake

For the yellow butter cake:

• 1  1/2 cups + 2 tbs (215 g) cake flour
• 1  1/2 tsp baking powder
• heaping 1/4 tsp salt
• 1/2 cup (1 stick) unsalted butter, room temperature
• 1 cup (200 g) sugar
• 1/2 tsp vanilla powder (if you don’t have this, just do 1 full tsp vanilla extract)
• 1/2 tsp vanilla extract
• 3 large egg yolks, room temperature
• 3/4 cup whole milk

For the chocolate cake:

• 1  1/4 cups (160 g) all-purpose flour
• 1/2 cup (50 g) unsweetened cocoa powder, non-Dutched
• 1  1/4 tsp baking powder
• heaping 1/4 tsp baking soda
• 1/2 tsp salt
• 1/4 cup + 1 tbs grapeseed or safflower oil
• 1 cup (200 g) sugar
• 1 large egg
• 1/2 large egg yolk
• 1 tsp vanilla extract
• 1/4 tsp almond extract
• 3/4 cup whole milk
• 1/2 cup strong, hot coffee

For the chocolate buttercream frosting:

• 8 oz bittersweet chocolate, chopped
• 6 oz (1 cup) semisweet chocolate, chopped
• 1/4 cup + 2 tbs egg whites, room temperature
• 3/4 cup sugar
• 1/8 tsp cream of tartar
• heaping 1/4 tsp kosher salt
• 1  1/2 cups (3 sticks) unsalted butter, room temperature
• 1  1/2 tsp vanilla extract
• 1  1/2 tsp espresso powder dissolved in 3/4 tsp hot water

For the vanilla buttercream frosting:

• 1/2 cup large egg whites, room temperature
• 1 cup (200 g) sugar
• 1  1/2 cups (3 sticks) unsalted butter, room temperature
• 1  1/2 tsp vanilla extract

For the semisweet chocolate glaze:

• 6 oz (1 cup) semisweet chocolate, chopped
• 1/2 cup heavy cream
• 1/4 cup light corn syrup
• 1 tsp vanilla extract
• 1/8 tsp salt

Other:

• 8-inch cake pan

Make the yellow butter cake:
Preheat 350°F. Grease and line the cake pan.

Sift together the cake flour, baking powder, and salt in a large bowl and set aside.

Cream the butter with the paddle attachment of your mixer on medium speed for about 2 minutes. Add the sugar and beat on medium-high until the butter is light and fluffy, about 3 to 5 minutes. Scrape down the bowl.

With the mixer on medium-low, add in the vanilla powder and extract, then the egg yolks one at a time. Scrape down the bowl again.

With the mixer on low, add the flour mixture in 3 batches, alternating with the milk and beginning and ending with the flour mixture.

Be careful to not overmix! Stop the mixer as soon as the last streaks of flour are incorporated into the batter.

Pour the batter into the prepared cake pan. Bake for 25-35 minutes, or until a cake tester comes out clean. Cool on a wire rack for 15 minutes, then turn the cake out of its pan to completely cool.

Make the chocolate cake:
Preheat the oven to 350°F. Grease and line the cake pan.

Sift together the flour, cocoa powder, baking powder, baking soda, and salt in a large bowl and set aside.

Beat the oil and sugar with the paddle attachment of your mixer on medium speed for about 2 minutes. Scrape down the bowl. With the mixer still running, add in the egg, egg yolk, vanilla, and almond extracts. Scrape down the bowl again.

With the mixer on low, add the flour mixture in 3 batches, alternating with the milk and beginning and ending with the flour mixture.

Be careful to not overmix! Stop the mixer as soon as the last streaks of flour are incorporated into the batter. Slowly pour in the hot coffee and mix until just incorporated.

Pour the batter into the prepared cake pan. Bake for 30-35 minutes, or until a cake tester comes out clean. Cool on a wire rack for 15 minutes, then turn the cake out of its pan to completely cool.

Make the chocolate buttercream frosting:
Put the chocolates in a heat-proof bowl and put it over a small saucepan of simmering water to make a double boiler. Stir the chocolates until they’re melted and set aside until cooled to room temperature.

With the whisk attachment, beat the egg whites, sugar, cream of tartar, and salt in the bowl of a mixer. Place the bowl of egg whites over the pan of simmering water and heat the egg whites until they are hot to the touch or 160°F. Return the bowl to the electric mixer and whisk on high speed for 5-10 minutes, or until the meringue is cool and holds a stiff peak.

With the mixer on medium speed, add the butter one tablespoon at a time. Scrape down the bowl, add the melted chocolate, vanilla, and espresso. Mix until the chocolate is completely blended in. If the buttercream seems very soft, allow it to cool, and beat it again.

Make the vanilla buttercream:
Whisk the egg whites and sugar in the bowl of a stand mixer bowl. Place the bowl over the pan of simmering water and heat the egg whites until they are hot to the touch or 160°F. Return the bowl to the electric mixer and whisk on high speed for 10-15 minutes, or until the meringue is cool and holds a medium-stiff peak.

Swap the whisk attachment to a paddle attachment and with the mixer on low, add the butter one tablespoon at a time. Then add in the vanilla and beat it on medium-high until the frosting is silky and fluffy.

Assemble the cake, part one:
Once the cakes are cooled, leveled, and split into 4 layers, it’s assembly time! Begin with the bottom yellow butter cake layer and spread a layer of the chocolate buttercream on top. Top it with another yellow butter cake layer, and spread another third of the chocolate buttercream on top.

Top with a layer of the chocolate cake and spread a layer of the vanilla buttercream on top. Add another chocolate cake layer.

Pop this into the refrigerator for 30 minutes to allow the cake and filling to set up.

Once the cake and filling are set, take it out of the fridge and frost the entire outside of the cake with the buttercreams, putting the chocolate on the bottom two layers and vanilla on the top two layers and top. Put this back in the fridge while you make the chocolate glaze.

Make the semisweet chocolate glaze:
Put the chocolate, corn syrup, and heavy cream in a microwavable bowl. Microwave in 30-second increments until the cream is steaming. Stir the chocolate until it is completely melted.

Stir in the vanilla and salt.

Let the mixture cool until it is thicker and syrup-like.

Assemble the cake, part two:
Slowly pour the glaze over the top of the cake, using an offset spatula to push it to and over the edge of the cake so that it runs down.

Decorate with marshmallows — or anything you want! After that, you can serve it right away. However, I find that cakes often improve in flavor and texture if you let them rest for a few hours. Set it out covered with a dome on a countertop for 4 hours or up to overnight.