To cap off my week-long blogiversary celebration, I knew some sort of fabulous dessert was in order.  After all, this is a very exciting occasion for me.  I only celebrate my blogiversary once every five years, apparently, so it will be five more before I do this again.  (Wonder where I’ll be in five years?)  As I often do when a special occasion arises, I decided to bake a cake.  But not just any cake.  I decided to revamp a layer cake that was formerly posted here on the blog that deserved some updating.  Now, I personally never had any trouble with that cake but a good number of readers reported back that the cake turned out dry for them.  Combined with the fact that the peanut butter frosting I had used for that version was good but not great, it needed a makeover.  I mean, a chocolate peanut butter layer cake really should be knock-your-socks-off, not just okay.

Addressing the issue of the dry cake layers was simple.  I turned to Baking Illustrated, my baking bible, for a cake recipe that I use often.  This recipe produces fudgy, moist cake layers thanks to one of my favorite ingredients in baking, sour cream.  Another plus is that the layers bake up essentially flat so there is no need to level the cakes (though this also means no cake scraps to snack on, so….)

Then, on to the frosting.  I briefly contemplated making a separate filling with different properties than the frosting used for the outside of the cake, but decided there was no need to overcomplicate things.  Peanut butter and chocolate are pretty great together and they don’t need all the bells and whistles.  I flew by the seat of my pants to create this frosting recipe, tasting as I went, until I was happy with the flavor and texture.  A fairly basic peanut butter frosting is lightened by folding in whipped cream to give it a silky smooth texture.  Happily, it made just the right amount for filling and frosting this cake.  Score!

My final tweak was to bake three 8-inch cake layers.  This is becoming my modus operandi for layer cakes these days, for a few reasons.  Cakes made with only two 9-inch layers are aesthetically displeasing (to me) because they are too wide compared to their somewhat stunted height.  I also do not tend to make cakes with two 9-inch layers that have been torted because I prefer the simplicity of not having to split cake layers (though admittedly I do think it is kind of fun).  I find cakes with three 9-inch layers simply too big.  So, this is why I continue to go with three 8-inch layers and why I think 8-inch cake pans are a totally worthwhile investment.

So there you have it – a special cake to celebrate a truly special occasion, at least to me.  Back when I started this blog, I never thought anyone would even read it, let alone try a recipe.  Thank you, all of you, so much for making this experience truly life-changing in many ways.  This cake is for you.

But….just in case the cake isn’t enough, I’ve got one more surprise up my sleeve.  Head on over to the giveaway page to see what I’m talking about!


For the cake:

  • 1¾ cups plus 2 tbsp. (9 3/8 oz.) all-purpose flour
  • 1½ cups (4½ oz.) unsweetened cocoa powder, plus more for dusting the pans
  • 1 tbsp. instant espresso or coffee powder
  • 1½ cups boiling water
  • ¾ cup sour cream
  • 1 tbsp. vanilla extract
  • 1½ cups (3 sticks) unsalted butter, at room temperature
  • 2½ cups plus 2 tbsp. (18 3/8 oz.) sugar
  • 3 large eggs, at room temperature
  • 1¼ tsp. baking soda
  • ¾ tsp. salt

For the filling and frosting:

  • ¾ cup heavy cream, chilled
  • 3¼ cups confectioners’ sugar, sifted, divided
  • 1½ cups (3 sticks) unsalted butter, at room temperature
  • 1 cup creamy peanut butter
  • 1 tbsp. vanilla extract
  • Pinch of coarse salt

To garnish:

  • Mini peanut butter cups, halved


  • 01

    To make the cake, preheat the oven to 350˚ F.  Butter the edges of 3 8-inch round cake pans and dust with cocoa powder, shaking out the excess.  Line the bottoms of the pans with parchment paper.  In a medium bowl, combine the cocoa powder, espresso powder, and boiling water.  Whisk until smooth; set aside to cool slightly.  When cooled down a bit, whisk in the sour cream and vanilla.  Set aside.  In the bowl of an electric mixer, beat the butter on medium-high speed until smooth, about 1 minute.  Gradually blend in the sugar and whip on medium-high speed until light and fluffy, 2-3 minutes more.  Blend in the eggs one at a time.  In a medium bowl, combine the flour, baking soda, and salt; whisk to blend.

  • 02

    With the mixer on low speed, add the dry ingredients in three additions alternating with the sour cream mixture, beating each addition just until incorporated.  Divide the batter evenly between the prepared pans.  Bake the cake layers for about 30-32 minutes or until a toothpick inserted in the center comes out clean, rotating the pans during halfway through to ensure even baking.  Transfer the baked cake layers to a wire rack and let cool in the pans at least 30 minutes before inverting onto the rack to cool completely.

  • 03

    To make the filling and frosting, combine the heavy cream and ¼ cup of the confectioners’ sugar in the clean bowl of an electric mixer fitted with the whisk attachment.  Whip on medium-high speed until light, fluffy, and stiff peaks form, being careful not to over mix.  Transfer the whipped cream to a separate bowl.  In the now empty mixer bowl fitted with the paddle attachment, combine the butter and peanut butter.  Beat on medium-high speed until smooth, about 45 seconds.  Add the remaining confectioners’ sugar to the bowl and mix in, slowly at first until incorporated, then increasing the mixer speed to high.  Blend in the vanilla extract and salt, and continue to whip on high speed until very fluffy, about 4-5 minutes, scraping down the sides of the bowl as needed.  Use a large spatula to gently fold about a third of the whipped cream into the peanut butter frosting.  Once the first addition has been evenly incorporated, gently fold in the remaining whipped cream until no streaks remain.

  • 04

    To assemble the cake, place one of the cake layers on a cake board or serving platter.  Spread an even layer of the frosting over the top of the cake.  Top with a second cake layer and another layer of the frosting.  Place the final cake layer on top.  Frost the top and sides of the cake using a thin crumb coat at first.  Place in the freezer for 30 minutes to set.  Reserve about 1 cup of the remaining frosting in a pastry bag fitted with a decorative tip (I used a Wilton #21).  Once the crumb cake is set, frost the top and sides of the cake again using an offset spatula for a smooth finish.  Use the reserved frosting to pipe a border around the base of the cake.  Pipe swirls evenly around the top border of the cake.  Finish by garnishing with halved peanut butter cups.  (I find that freezing the candy for an hour or so beforehand helps them unwrap and cut while still looking nice.)  Refrigerate the cake until ready to serve.

  • 05

    To make the cake in two 9-inch pans, reduce the amount of batter by one third.
    To make the cake in three 9-inch pans, increase the amount of batter by one third.
    The baking times for alternate sizes may differ, so use the toothpick test to monitor doneness.

    For tips on frosting your cake, see this post about crumb coats and this about smoothly frosting a cake.  Also, I think this revolving cake stand is invaluable.