Sheet Pan Chocolate Birthday Cake

Preheat the oven to 350 degrees F. Grease and line one 9x13 cake pan with parchment paper.

Soak cake strips in ice cold water.

In a medium bowl, whisk together the flour, sugar, cocoa powders, baking powder, and salt. Set aside.

In a large bowl, whisk together the milk, oil, eggs, and vanilla.

Add the dry ingredients to the wet and whisk until just combined.

Lastly, whisk in the hot coffee until fully combined.

Pour half of the cake batter into the prepared pan (or divide between two 9x13 pans) and wrap the soaked cake strips around the outside of the pan. Weigh the batter for even cake layers.

Bake for about 20-25 minutes or until a toothpick inserted comes out clean the cake pulls away from the sides of the pan.

Turn the cake out onto a wire rack to cool completely. Repeat with the remaining half of the cake batter.

Wrap the cake layers with plastic wrap and set aside until ready to assemble.

Wipe the bowl of a stand mixer and whisk attachment down with white vinegar.

Add the egg whites and sugar to the bowl and whisk until fully combined.

Place over a small saucepan of simmering water, and whisk frequently until it reaches 160 degrees F or until the sugar is completely dissolved and the mixture no longer feels grainy.

Move the bowl over to the stand mixer with the whisk attachment. Whisk on medium-high speed until medium peaks form.

Add the vanilla and continue whisking until stiff peaks form.

Turn the mixer down to low speed, and wait until the meringue cools down to at least 85 degrees F.

Cut the butter into cubes and add to the meringue a few pieces at a time, allowing them to fully incorporate before adding more.

Once all of the butter is added, it may look curdled, but keep beating for a few more minutes and it will come together.

Once the buttercream has mostly come together, change the whisk attachment to the paddle and keep mixing on low speed until homogenous and smooth.

Lastly, mix in the melted chocolate on low speed until fully combined.

Place the first cake layer on a serving tray. Add eight 3 tablespoon scoops of buttercream and spread into an even layer. Place the second cake layer on top and repeat.

Spread an even layer of buttercream on the sides, then chill in the fridge for at least 10 minutes.

Remove the cake from the fridge and apply a thicker layer of buttercream to the sides.

Pipe buttercream along the edges of the cake as desired, then place in the fridge or freezer while you make the ganache.

In a small saucepan, place the heavy cream over low-medium heat. Stir frequently with a rubber spatula, and bring to simmer, or about 190 degrees F.

Remove the pan from heat and add the chocolate and butter, and gently stir with a rubber spatula until fully combined.

Immediately pour the warm ganache onto the cake and spread into an even layer. Allow to set at room temperature or in the fridge before slicing.