Mini vanilla cake with buttermilk ermine frosting (plus a smash cake!)

first birthday cake plus smash cake

Last week we celebrated Isabelle’s first birthday. As I’ve looked back on the photos and videos from this past year and cheered her on as she’s started taking her first steps, I realize — despite the seeming never-endingness that is 2020 — time marches on.

Naturally, there was cake. We’re still sticking to very small gatherings here, so I made a petite birthday cake and a very petite one for Isabelle to “smash.” (Though let’s be honest — this is our third kid and this was hardly her first taste of cake!) It was the perfect size.

Buttermilk Ermine Frosting

Let’s talk for a minute about the buttermilk ermine frosting. If you’ve never made ermine frosting (sometimes called flour buttercream or boiled icing… uh, yum?) you really must try it! It’s fluffy and not too sweet, almost like a sturdy whipped cream in texture. This old-school frosting starts with a flour-milk-sugar roux that’s cooked to a thick paste on the stove. Once cooled, it’s beaten together with softened butter. I promise, it’s much tastier than it sounds! Ermine frosting is softer than Swiss meringue buttercream so it’s not the best for super sharp edges and intricate piping, but it’s tops for eating. Using buttermilk instead of regular milk gives it cream cheese frosting vibes; I’m totally using it the next time I make a red velvet or carrot cake!

A few notes:

  • The measurements for this cake are a bit odd because it’s scaled down / adapted from this old favorite vanilla cake recipe. The cup conversions are super awkward so I’ve just stuck with grams. I recommend baking by weight whenever possible — it’s much more accurate and quicker/cleaner than breaking out all the measuring cups! A scale is truly my favorite kitchen tool and a worthwhile investment.
  • To make the cakes pictured, I split the batter among two 6-inch cake pans and two 4-inch cake pans. For the most even layers, weigh the batter (told you the kitchen scale is handy!). Here’s how I do it: before baking, I weigh the bowl in which I’ll be mixing my batter. After I’ve finished mixing my batter, I’ll weigh the bowl with the batter, then subtract the weight of the bowl to find out how much my batter weighs. Then I divide the batter weight by however many pans I’m using. In this case, I first divided by 3 — this is how much batter I put in each of the two 6″ pans. Then I divided the remaining third of the batter between the two 4″ pans. Note that if you’re using different sized pans, they may bake at slightly different rates; though in this case all my layers finished around the same time. Not making a smash cake? You can just use three 6″ pans!
  • If you don’t have buttermilk, you can substitute plain milk (either lowfat or whole should work nicely) for a plain, delicious vanilla frosting.

Mini vanilla cake with buttermilk ermine frosting (plus a smash cake!)

Makes one 2-layer 6″ cake plus one 2-layer 4″ smash cake (or one 3-layer 6″ cake)

Ingredients:

For the vanilla cake:

  • 119g all-purpose flour
  • 136g cake flour
  • 1 1/4 tsp baking powder
  • 1/8 tsp baking soda
  • 1 tsp kosher salt
  • 250 g granulated sugar
  • 3 large eggs, at room temperature
  • 204g sour cream, at room temperature
  • 2 tsp pure vanilla extract
  • 136g unsalted butter, at room temperature
  • 60g neutral vegetable oil (I prefer grapeseed)

For the buttermilk ermine frosting:

  • 42g all-purpose flour
  • 140g granulated sugar
  • 1/2 tsp kosher salt
  • 255g buttermilk
  • 240g unsalted butter, at room temperature
  • 2 tsp pure vanilla extract

To assemble:

  • About 1/3 cup peach preserves (or other thick fruit jam)
  • Sprinkles, for decorating

Method:

For the vanilla cake:

  1. Preheat the oven to 350F (175C) with a rack in the middle position. Line the bottom of two 6″ pans and two 4″ pans with parchment paper, then grease and flour the pans.
  2. In a glass measuring cup with a spout, whisk together the eggs, vanilla, and 50 grams of the sour cream.
  3. In the bowl of a stand mixer fitted with a paddle attachment, combine the flours, baking powder, baking soda, salt, and sugar. Mix on low for 30 seconds to combine.
  4. With the mixer still on low, add the butter a spoonful at a time, followed by the oil and the remaining 154 grams of sour cream. Once all the flour is moistened, increase the speed to medium and beat for about 90 seconds. The batter will be very thick at this point. Scrape down the sides of the bowl and paddle.
  5. With the mixer on low, add half of the egg and sour cream mixture. Increase the speed to medium and beat for 30 seconds. Scrape down the sides of the bowl and paddle. Repeat with the remaining egg mixture.
  6. Fold the batter a couple of times with a flexible spatula to ensure everything is well incorporated. Divide the batter among the prepared pans (see notes above) and smooth the surfaces with a small offset spatula. Place the pans on a baking sheet.
  7. Bake until the cakes are puffed and springy, and a skewer inserted in the middle comes out clean, about 28-35 minutes. (These cakes don’t brown much.) Cool 10-20 minutes in pan and then turn out to a cooling rack. For easiest assembly, wrap each layer in plastic wrap and chill in the refrigerator completely before filling and frosting.

For the buttermilk ermine frosting:

  1. In a medium saucepan, whisk together the flour, sugar, and salt until well combined. Add the buttermilk and whisk until smooth.
  2. Cook the mixture over medium-low heat, whisking constantly, until it comes to a boil. One the mixture starts boiling, cook for an additional two minutes. It should be thick and glue-like; if you run a spoon through the middle of the mixture, the line should remain for a second before slowly filling again.
  3. Remove from the heat and use a flexible spatula to scrape into a pie plate (using a wide, shallow pan speeds the cooling process). Press a piece of plastic wrap against the surface to keep a skin from forming. Cool completely to room temperature before proceeding.
  4. Place the butter in a bowl of a stand mixer fitted with the paddle attachment. Beat on medium until very light and fluffy, about five minutes. Add the cooled pudding a spoonful at a time. Once all the pudding has been added, scrape down the paddle and sides of the bowl. Continue mixing until smooth.
  5. Switch to the whisk attachment and add the vanilla. Whip on medium speed until thick, smooth, and creamy, about 3 more minutes. Use immediately or transfer to an airtight container and refrigerate for up to one week (or freeze for up to 6 months). Bring back to room temperature and rewhip before using.

To assemble:

  1. If you plan to pipe words or other decorations on your cakes, set aside a small amount of buttercream (I only needed a couple spoonfuls to pipe “One” and “1”). Transfer about 1 cup of buttermilk ermine frosting to a piping bag fitted with a large round tip. Level the cakes if needed using a sharp serrated knife or cake leveler. Place one 6-inch round on a cake board or serving platter. Pipe a dam around the edge and fill the center with peach preserves. Place the second layer cut side down. Frost the entire cake with a thin layer of frosting to lock the crumbs in, then chill for about 15 minutes. Repeat process with the 4″ cake layers.
  2. Frost the cakes and decorate as desired. I tinted my reserved frosting with a drop of Americolor Dusty Rose and piped the text using a #2 Wilton tip (I recommend practicing a couple times on a piece of parchment paper). Cake is best enjoyed at room temperature.

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