The Cake Slice Bakers January 2013 - Banana Cake with Coffee Walnut Buttercream

I can't believe how quickly the time has gone by.  It seems like only yesterday that December's cake was being voted upon and baked.  Here we are in a new year and we actually had a tie in the voting between The Classic and Banana Cake with Coffee Walnut Buttercream so we were able to chose which one we wanted to bake.  Since I am a huge fan of banana cake it was an easy choice for me, although I will probably bake The Classic at a later time.

We always seems to have an abundance of bananas in our house, so it was easy to grab a few extra-ripe ones for my cake.  I decided to bake the cake on one day and refrigerated the layers overnight, and then make the buttercream and assemble the cake next day, which worked out really well.

Since my girls aren't huge fans of walnuts I decided to change the frosting a little bit. I saw that Vintage Cakes also had a recipe for Coffee Buttercream (1 tablespoon instant espresso and 2 teaspoons of water to make a paste and add to basic buttercream) so I went with that and also added ⅓ cup of melted dark chocolate so I ended up with a Mocha Buttercream.  I also decorated the top of the cake with chocolate covered coffee beans, well I decorated the top with what I had left because I seriously can't stop eating them once I start.  I used the basic buttercream recipe from the book which is slightly different to the coffee walnut buttercream.

At first I found it difficult to find a saucepan that I could put the metal bowl of my mixer into without it touching the water.  My solution was to get out my pasta pot that has a metal insert to drain the pasta.  I filled it just until the water reached the insert, I turned the insert handles in towards each other, and then I balanced my mixer bowl on the top of the insert handles, slightly tilting the bowl.  By doing this the water could simmer away without the bowl touching the water.

This type of buttercream is known as a Swiss Meringue Buttercream, and I was looking forward to trying it since I had only made a regular buttercream previously.  It is funny when you shy away from attempting something because you think it sounds too difficult, and then when you try it you wonder what all of the fuss was about.  That is what happened to me with this buttercream.  I am such a baking nerd that I was even excited when it curdled (just as the author said it would) and then came back together again.  The end result was a deliciously fluffy mocha-flavored buttercream.

As I was assembling the cake I realized that I should have trimmed it a little as the layers had baked up a little uneven, but I had already topped it with the last layer so I pressed on.  In the end the cake was a little lopsided but I think it gave it character.  Well, that is what I told myself and I knew that it wasn't going to affect the taste of the cake.  And a few chocolate-covered coffee beans on top sealed the deal.

This cake was definitely a winner.  The cake had a deep banana flavor and the mocha buttercream was a nice accompaniment to it.  It is the sort of cake that you could top with so many different flavors and it would still be great.

Click here to check out the blogs of my fellow Cake Slice Baker's to see which cake they chose to bake - was it The Classic or the Banana Cake with Coffee Buttercream?


Banana Cake with Coffee Walnut Buttercream
(Printer Friendly Recipe)

Ingredients
Cake

• 2½ cups all-purpose flour
• 1½ teaspoons baking powder
• ¼ teaspoon baking soda
• 1½ cups mashed ripe bananas (about 3)
• ¾ cup buttermilk, at room temperature
• 1 cup unsalted butter, at room temperature
• 2 cups sugar
• 1 tablespoon pure vanilla extract
• 4 eggs, at room temperature

Coffee Walnut Buttercream

• 1 cup toasted chopped walnuts
• ¼ cup corn syrup
• ¼ cup bourbon
• 2 tablespoons instant espresso powder
• 5 egg whites
• 1¼ cups sugar
• ¼ teaspoon cream of tartar
• 1½ cups unsalted butter, at room temperature
• ¼ teaspoon of fine sea salt

Preparation
Cake

1. Center an oven rack and preheat the oven to 350℉.
2. Grease three 8 by 2-inch round cake pans, and line the bottom of the pans with parchment paper circles.
3. In a large bowl sift together the flour, baking powder, salt, and baking soda, then whisk the ingredients with a hand whisk.
4. In a small bowl combine the banana with the buttermilk.
5. In the bowl of a stand mixer fitted with a paddle attachment cream the butter, sugar, and vanilla together on high speed until fluffy, about 5 minutes, stopping the mixer frequently to scrape the sides and the paddle with a rubber spatula.
6. Blend in the eggs one at a time.
7. With the mixer on low add the flour mixture in three parts, alternating with the banana mixture in two parts, beginning and ending with the four.   After each addition scrape the bowl well.  Stop the mixer before the last of the flour has been incorporated and complete the blending by hand with a rubber spatula.
8. Divide the thick batter equally among the prepared pans, and tap the pans on the counter to settle.
9. Bake until the centers spring back when lightly touched, 28 - 30 minutes.
10. Cool the cakes in their pans on a wire rack for 30 minutes.  Flip them out and let them continue to cool on the rack, top side up, until they reach room temperature.  Leave the parchment paper on until you assemble the cake.
11. To assemble the cake lay one of the cakes top side up on a cake plate.  Using a metal spatula frost the top with ¾ cup of buttercream out to the edge of the cake (filling will be about ¼ inch thick).  Stack the second cake top side up on top of the frosted cake and spread another ¾ cup of buttercream on top of it.  Stack the last layer of cake top side up on top.  Look for any frosting that may have oozed out the sides and spread it along the sides of the cake.  Apply a thin layer of frosting all over the cake to create a "crumb coat".  Place the cake in the refrigerator until the frosting is firm, about 10 minutes.  Take it out and frost the cake with the remaining buttercream, using your spatula to make decorative swirls.

Buttercream
Walnut-Espresso paste

1. Puree toasted, chopped walnuts in a food processor until they just begin to form a paste. 
2. Add corn syrup, bourbon, and espresso powder and blend until combined.  Set aside.

Basic buttercream:

1. Using a hand whisk, whisk together the egg whites, sugar, and cream of tartar in the bowl of a stand mixer.
2. Place the bowl over (not in - do not let the bowl touch the water) a saucepan of simmering water.  The egg mixture will be gloppy and thick, but as the mixture begins to warm, it will become more fluid.
3. Continue to gently whisk the mixture until it is very hot to touch (130℉ on a candy thermometer).
4. Move the bowl to the stand mixer and, using the whisk attachment, whip the whites on medium-high speed until they have tripled in volume and are thick and glossy and hold stiff peaks (like meringue).  Turn the mixture down to medium-low speed until the mixing bowl is just cool to touch, 1 to 2 minutes.
5. Kick the mixer back up to medium-high speed and and add the butter one piece at a time, adding the next piece just as the previous one has been incorporated.Stop the mixer every every now and again to scrape down the sides. At some point the buttercream will appear curdled, but this is normal, so keep mixing until it all comes together again.
6. Once all of the butter has been incorporated and the frosting is fluffy and creamy, add the vanilla and salt and mix until fully combined.
7. Covered with plastic wrap this frosting will last 2 days at room temperature or 7 days in the refrigerator.  If refrigerated, the frosting will need to come to room temperature before use, and will need to be re-whipped (by hand if at room temperature, or machine if refrigerated), before frosting a cake.

Cake from Vintage Cakes by Julie Richardson, adaptations by All That's Left Are The Crumbs.