Fudgy Chocolate Sheet Cake

October is a great month. The weather really starts to turn towards fall. The mornings and evenings are cool, the days perfect and everyone still wants to be outside. There are two added, personal, bonuses in the month of October. The first is James’s birthday! The second is my grandmother’s birthday! James and Grandma Doe are 3 days and 57 years apart yet can still share the same delicious cake (see adorable photo below).

When you hear ‘sheet cake’ you may think of an overly sugary, dry cake from the grocery store that seems like it’s been sitting there a little too long. This sheet cake proves that stereotype wrong. It is fudgy and rich and you want to keep grabbing a small forkful from the cake plate after you’ve eaten your slice of cake. The one thing I would change next time is to use less sugar in the vanilla buttercream frosting. It was almost cloyingly sweet. Other than that, keep everything else as is. So, so good. Even if you make this for a non-birthday celebration, people will feel like their birthday came early after taking a bite!


Source: Smitten Kitchen
Cake layers
1 cup (2 sticks) unsalted butter, at room temperature
2 cups firmly packed dark brown sugar
2/3 cup granulated sugar
4 large eggs
2 cups buttermilk
2 tsp. vanilla extract
2 3/4 cups (345 grams) all-purpose flour
1 1/3 cups (115 grams, approximately) Dutch-process cocoa
1/2 tsp. baking soda
1 tsp. baking powder
3/4 tsp. table salt

Fudge buttercream filling
2 ounces unsweetened chocolate, melted and cooled
1 1/2 cups confectioners’ sugar (no need to sift)
1/2 cup (1 stick) unsalted butter, at room temperature
2 tablespoons half-and-half or whole milk
1 teaspoon vanilla extract

Vanilla buttercream frosting
NOTE: these proportions are from the original recipe so feel cut back the sugar by 1/4-3/4 cup.
1 cup (2 sticks) unsalted butter, at room temperature
3 3/4 cups (1 1-pound box) powdered sugar, sifted
4 tablespoons half-and-half or whole milk
2 teaspoons vanilla (use less if you want a whiter frosting)

Heat oven to 325°F. Grease and line the bottom of two 9×13 rectangular cake pans with parchment paper.

Make cake layers

  1. Using an electric mixer, beat butter with sugar in a large bowl until light and fluffy. Add eggs, one at time, beating each in until just incorporated and scraping down sides of bowl. Add vanilla, then buttermilk. (Don’t worry if the batter looks a uneven and grainy; it will all be fine in a minute.)
  2. Place flour, cocoa powder, baking soda, baking powder and salt in a sifter over the mixing bowl and sift ingredients in.
  3. Beat or stir dry ingredients into batter until just combined; scrape down bowl again. Divide batter between two pans. Bake each layer for 30 minutes. Cakes are ready when a toothpick inserted into the center of each layer comes out batter-free.
  4. Cool in the pan 10-20 minutes, then remove cakes from pans and let cool completely on racks. You can put those racks right into the freezer for about 10 minutes to firm up this very soft and tender cake before leveling and frosting it; it makes the process much easier.

Make fudge buttercream filling

  1. Add the butter to a medium bowl and beat the butter until light and fluffy with an electric mixture, then add the sugar and melted chocolate, followed by the milk or cream and vanilla. With an electric mixer, it helps to sift the powdered sugar first.

Make vanilla buttercream

  1. Beat the butter until light and fluffy in a large bowl. Add sugar 1/2 cup at a time (trust me on this, it allows us to get away with less sugar than the standard recipe) until fully incorporated. Beat in half-and-half/milk then vanilla.

Fill & Finish cake

  1. Remove first cooled cake layer from freezer. Lay the cake top down on the serving tray. Spread fudge buttercream filling evenly over first cake layer. Place second layer on top of filling; you can level this too slightly if it it has dome, but it’s less essential to the stacking of the cake if it’s the top layer.
  2. Cover the cake with the vanilla buttercream frosting


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