Fudge Brownie Filled Buttermilk Cake with Brown Sugar Marshmallow Frosting

I saw a recipe a few weeks ago for a Vintage Cake.  It looked super amazing, and I wanted to try it out, but with a few changes. First, I really wanted my brownie layer to be in the middle of the cake, sort of replacing the filling.  Second, I wanted to use a slightly lighter frosting, something not too heavy and dense, so I settled on a brown sugar marshmallow frosting (which my entire family loves!).  The buttermilk cake layers are moist, flavorful, and delicious while the fudge brownie filling is a rich and dense chocolate layer.  The marshmallow frosting is smooth and fluffy and just the right touch to finish it off!  Note:  The brownies will need time to cool completely and chill in the refrigerator, so plan ahead!

Fudge Brownie Filled Buttermilk Cake with Brown Sugar Marshmallow Frosting

Fudge Brownie Layer:
1/2 cup canola oil
1 cup granulated sugar
1 teaspoon vanilla extract
2 eggs
1/2 cup all purpose flour
1/4 cup +2 Tablespoons cocoa powder
1/4 teaspoon baking powder
1/8 teaspoon salt
7 ounces (1/2 of a 14 ounce can) sweetened condensed milk
2 ounces (1/3 cup) semi sweet chocolate chips

Buttermilk Cake:

2 1/3 cups cake flour (Or sub 2 cups +3 Tbsp all-purpose flour and 2 Tbsp cornstarch)

1 1/2 teaspoons baking powder

1/2 teaspoon baking soda

1/4 teaspoon salt

12 Tablespoons (1 1/2 sticks) butter, room temperature

1 1/3 cups granulated sugar

3 eggs

1 1/2 teaspoons vanilla

1 cup buttermilk
Brown Sugar Marshmallow Frosting:

1 cup brown sugar (packed)

1/4 cup water

1/2 cup corn syrup

4 egg whites

2 tsp vanilla

Preheat the oven to 350F.  Spray a 9 inch round cake pan with cooking spray, then line the bottom with parchment paper and spray the parchment.  Set aside.

In a large bowl, whisk together the oil, sugar, vanilla, and eggs until well blended and smooth.  Add the flour, cocoa powder, baking powder, and salt, and stir until combined and no streaks of flour remain.  Pour the batter into the prepared pan and smooth the top.  Bake for 18 to 20 minutes, or until a toothpick inserted in the center comes out clean.  Do not overbake, or the brownies will be too hard to cut through in the cake. 

While the brownies are baking, place the condensed milk and chocolate chips in a microwaveable bowl and heat in 30 second intervals, stirring after each, until melted and smooth.  When the brownies are done, remove from the oven and immediately pour the condensed milk mixture over the top of the brownies, spreading all the way to the edges.  Let cool completely, then chill until cold.  When the brownies are cold, run a knife around the edge of the pan and carefully lift the brownie layer out of the pan.  Set on a plate, cover with plastic wrap, and set aside while you make the cake layers.

For the cake, preheat the oven to 350F.  Spray 2 9-inch round cake pans with cooking spray. Set aside.

In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt.  

In a large bowl, cream together the butter and sugar until well blended and smooth.  Add the eggs and vanilla, and beat for 2 to 3 minutes, or until fluffy.  Beat in 1/3 of the flour mixture until just combined, followed by half of the buttermilk.  Add another 1/3 of the flour mixture, followed by the remaining buttermilk.  Beat in the remaining flour until just combine.  

Pour the batter evenly into the two prepared pans and smooth the tops.  Place in the preheated oven and bake for 20 to 22 minutes, or until a toothpick inserted in the center comes out clean.  Remove cakes from the oven and let cool in the pans for 10 to 15 minutes.  Carefully turn the cakes out of the pans and let cool completely on a cooling rack.  

For the brown sugar marshmallow frosting, mix brown sugar, water and corn syrup in a medium saucepan. Bring to a full rolling boil. (Be careful, as it will rise, so make sure the sides of your pan are taller). Let it boil at medium to medium high until the syrup reaches 240F. Meanwhile in a stand mixer, beat egg whites until stiff.

Slowly pour the hot syrup in a thin stream into egg whites, beating constantly. Beat until icing holds peaks, then blend in vanilla.

To assemble the cake, place a buttermilk cake layer on a serving plate.  Spread with a thin layer of the frosting.  Place the brownie layer on top.  Spread with another thin layer of frosting.  Place the second cake layer on top and frost the top and sides with the remaining marshmallow frosting.  Makes 16 servings.  

Enjoy!  -Cardamommy