Blackberry Supreme Cake

Last week was my mother's birthday.  Of course, I was not here to celebrate with her on her actual birthday so made a cake and dinner this week.  I've been thinking about this cake for a while now.  I knew I wanted it to feature berries and I decided on blackberries because we have a freezer full of them from last summer.  I also knew I wanted it to be three layers, because I love cakes with lots of filling.  The rest of the cake was created on the go as I thought about what would be good.  So here we go.  The blackberry supreme cake, three layers of white cake, filled with blackberry and cream cheese mixture filling, and iced with a blackberry Swiss meringue buttercream.  This will make A LOT of frosting so if you're not planning on piping roses or ruffles or something else you should halve the recipe.

Cake (yields 3 9-in cakes)

4 ½ cups cake flour

3 teaspoons baking powder

¾ teaspoon salt

2 ¼ cups of unsalted butter

3 ½ cups sugar

1 teaspoon pure vanilla extract

1 ½ cups milk

12 egg whites

Cream Filling

8oz cream cheese

2 tablespoons heavy cream

¼ cup sour cream
⅓ cup sugar

Fruit Filling

16 oz. frozen blackberries, thawed
1/3 cup sugar
3 tbsp. cornstarch
1 tsp. lemon juice

Blackberry Swiss Meringue Buttercream

10 egg whites

2 ½ cups sugar

Pinch of salt

3 cups unsalted butter

1 tablespoon and 1 teaspoon pure vanilla extract

⅔ cup blackberry purée

Directions

1. Preheat oven to 350 degrees.  Grease three 9 by 2 inch round cake pans, line them with parchment paper and grease again.


2. In a medium bowl, sift together the flour, baking powder, and salt.  Set aside.  In the bowl of an electric mixer fitted with a paddle attachment, beat the butter and 3 cups of sugar until light and fluffy, about 3-4 minutes.  Beat in vanilla.  With the mixer on low speed, add the flour mixture in three parts, alternating with the milk, beginning and ending with the flour.  Transfer the batter to a large bowl and set aside.

3. In a very clean bowl of an electric mixer fitted with the whisk attachment, beat the egg whites on low until foamy.  With mixer running, gradually add the the remaining sugar and beat on high speed until stiff, glossy peaks form, about 4 minutes.  Gently fold a third of this egg-white mixture into  the butter batter until combined.  Gently fold in the remaining whites.

4. Divide the batter evenly between the three prepared pans.  Bake, rotating the pans halfway through, until the cakes are golden brown and a toothpick inserted in the centers come out clean.  About 30-35 minutes.  Transfer the pans to a wire rack and let cool for about 20 minutes before inverting the pans and letting them cool completely, top sides up.

5. Blackberry Filling: To make the blackberry filling, drain the thawed berries, reserving the juice in a liquid measuring cup.  Add enough water so that the total liquid equals 1¼ cups.  Add the liquid to a medium saucepan with the sugar and cornstarch.  Heat over medium-high heat, whisking occasionally, until the mixture begins to bubble and thicken.  Continue whisking so no lumps form.  Once thickened, remove from the heat and whisk in the lemon juice.  Fold in the drained berries with a spatula.  Cover and chill until ready to use.

6. Cream Filling: In the bowl of an electric mixer fitted with a paddle attachment, beat the cream cheese, sour cream, sugar, and whipping cream until smooth.  Let chill.

7. Frosting: Clean the (heat-proof) bowl of the electric mixer.  Add the egg white and sugar and set over a pot of simmering water, whisking constantly until the temperature reaches 160 degrees, or until the sugars has completely dissolved and the mixture is hot.

8.  Transfer the bowl back to the mixer fitted with a whisk attachment, whip until the meringue is thick, glossy and and the bowl feels neutral to the touch.  When the bowl is neutral to the touch (do not start adding butter if it is still warm) switch over to the paddle attachment and begin adding the butter cubes, one at a time, until incorporated and the mixture has reached a silky smooth texture.  If it curdles keep mixing it, it will come back together.  Add the vanilla, salt, and slowly add the blackberry puré.

9. Assembly: To assemble the cake, place a cooled cake on a cake board or on serving platter.  Spread half of the cream mixture over the first layer, making sure to reach the edge.  Spoon some of the blackberry filling over the cream.  Top with the next layer and repeat the process.  Top with the last layer and refrigerate until chilled.  Apply a crumb coat of frosting and refrigerate.  Frost as desired I used this tutorial as a guide. 

Cake adapted from Martha Stewart, filling adapted from Annies-Eats, frosting adapted from Sweetapolita.