White Cake for the Dark Side: White Mountain Cake with Marshmallow Buttercream

I had the opportunity to bake my cousin's son Josh a second birthday cake for his ninth birthday. It was for a party with a Star Wars theme and Josh requested for a dark side cake. Josh prefers vanilla cake to chocolate, so I was able to try a cake that's been on my to-bake list for a while: the White Mountain Layer Cake with Marshmallow Buttercream from BraveTart by Stella Parks.

This white cake recipe -- which Stella loosely based on one printed in 1858 -- has some distinctive features. It includes not only buttermilk, but also virgin coconut oil, which Stella says "amplifies the aroma of butter and vanilla while creaming up lighter (and whiter) than butter alone." Stella says the result is "rich and velvety to the point of creaminess, heady with vanilla, and almost as fluffy as an angel's food cake."

To make the cake batter, you cream room cool butter with coconut oil, sugar, baking powder, baking soda, and salt until light and fluffy; add egg whites, vanilla extract, and almond extract; and alternately add sifted cake flour and room temperature buttermilk. The raw batter had a strong coconut aroma. I divided the batter between three parchment-lined 8-inch pans and baked them for 40 minutes. Although the recipe says they should have an internal temperature of 210 degrees, mine had a temperature in the mid 190s and I was confident that they were done (I also baked the brown butter carrot cake from BraveTart to only 195 degrees).

The buttercream recipe for this cake is essentially homemade marshmallow creme whipped with butter; it is based on a 1896 recipe by Janet McKenzie Hill that used store-bought marshmallows. Stella says that using marshmallow instead of egg white meringue as a buttercream base removes the any inherently eggy aftertaste and improves the buttercream's shelf life -- to up to a week at room temperature. The marshmallow buttercream is also more stable than meringue buttercream and can incorporate a greater volume of liquid additions (e.g., melted chocolate, fruit puree). While these are real benefits, marshmallow buttercream is a bit more work and requires some advance planning. I made the marshmallow creme the day before baking the cake because it requires some waiting time.

To make the marshmallow creme, you heat a mixture of water, corn syrup, sugar, and salt to 250 degrees; cool the mixture to precisely 212 degrees; add a mixture of vanilla bean seeds and gelatin softened in water; and whip the mixture until thick and tripled in volume. You pour the marshmallow into a greased container, cover it, and let it stand a room temperature for at least two hours and up to a week. When you're ready to make the frosting, you whip the marshmallow creme and slowly add cool butter.
I leveled the cooled cake layers, filled and frosted the cake with the marshmallow buttercream, and covered it in homemade rolled fondant. Even though I was making a dark side-themed cake, I didn't want a predominantly black color scheme; I think black food coloring is unappetizing. I decided to go with a light blue marbled fondant instead (it was a mix of blue, purple, and a little black), with blue and black accents. And since my fondant sculpting skills are terrible and I didn't have the benefit of my brother's artistic talents (he sculpted me a fondant Yoda and a fondant Chewbacca for two Star Wars cakes last year), I took the easy way out and decided to use a Funko figurine of Kylo Ren in a TIE fighter as the primary decoration. I cut the letters using a set of alphabet cutters I bought off of Etsy, and used homemade edible glue to affix silver star sprinkles (they are by Wilton and I bought a small bag of them at Michael's for $1).
This is an outstanding white cake. It has a very tight, even crumb, but is light and velvety -- exactly as Stella says, almost to the point of creaminess. The coconut oil and almond extract add a floral note to the flavor, but it's subtle. The buttercream tasted like marshmallow and when I tried it plain, my first reaction was that it was too sweet -- but as part of the assembled cake, the sweetness level was fine. I can't say that this buttercream tasted better than than Rose Levy Beranbaum's mousseline (an Italian meringue buttercream) that I normally use; I have never noticed an eggy aftertaste with the mousseline. However, the extended shelf life of the marshmallow buttercream is a real advantage.

Beranbaum's mousseline has a shelf life of two days at room temperature, which is why I've always used it for cakes covered in fondant that I don't want to refrigerate before serving. It's nice to have another option for a buttercream that can be stored at room temperature for an extended length of time, and I am very interested in trying some of Stella's flavor variations on both this cake and the marshmallow buttercream. Specifically, she says that the cake her brother requested for his wedding was a hazelnut version of the cake paired with a milk chocolate version of the buttercream; that particular combination sounds heavenly to me. But even the plain vanilla versions of both were fantastic.

Recipe: "White Mountain Layer Cake with Marshmallow Buttercream" from BraveTart by Stella Parks, recipe available here at saveur.com.

Previous Birthday Cakes for Josh:


Sally said…
I agree - I made this 6 mths ago for a baby shower and LOVED it.
I hope that I can try all of the cake recipes from BraveTart!