There’s kind of nothing I like more than chocolate cake with pink frosting. Maybe it’s because I am super into the pink and brown color combo. I don’t know, but to me, chocolate cake tastes exponentially better when iced with something pink. Thus, it should come as no surprise that when my younger son and I began our annual birthday cake discussion, and he revealed to me that he was hoping for chocolate cake with some kind of strawberry vibe, I was ecstatic, as i knew that if the strawberries made their way into the icing, we’d have pink frosting in the house. That’s when these chocolate cupcakes with strawberry marshmallow frosting were born.
As he unpacked his vision of the perfect 10th bday cake, and we pondered how exactly the strawberries were going to make their way into (or onto) the cake, we both concluded that we probably had no choice but to put them in the frosting, as we’d be having cupcakes at the party rather than a traditional layer cake. Cupcakes were a necessity as the celebration was to take place at a paintball park (FYI regarding paintball: never again), and even though we both kind of loved the idea of sliced strawberries layered throughout a chocolate cake, we agreed to forego them for a strawberry flavored frosting, instead. Now, still reeling (in a good way) from the book launch party of Icebox Cakes, I decided to give myself a break on the recipe development front, and use my recipe for extra moist and chocolate-y birthday cake for the chocolate cake component of my son’s bday treat, as, really, why mess with a good thing? I was very close to just flavoring my go-to old school buttercream with strawberry puree and calling it a day/bday. 
But after having made about 50 mini s’more icebox cakes for said party the week prior, I was kind of excited to try a marshmallow frosting of some kind (the s’more cake features a marshmallow whipped cream and I had marshmallow on the brain). My bookshelf/internet research began with a search for “seven minute frostings,” aptly named for the amount of time one must beat the ingredients before marshmallow-y-ness is achieved. I began with this seven-minute frosting, which brought me to Martha Stewawrt’s book and to Smitten Kitchen, and, honestly, once I read the Smitten recipe, I knew developing my own recipe was not going to be rocket science. Not only was Deb’s recipe super simple (which, really, they all are) but her technique was genius in that you just add all your ingredients together and start beating them over a double boiler until you’re looking at a big bowl of fluffy, billowy marshmallow. 
No adding your flavoring later, as in this Joy of Baking coconut cake recipe, no doing half the beating on the flame and half off, as in this Epicurious recipe, and because it’s Smitten Kitchen, you know the recipe is going to work. As for the strawberry dimension of my marshmallow frosting, I found an orange frosting recipe and a strawberry heavy recipe super helpful, as I wasn’t exactly sure how a marshmallow frosting was going to react to the addition of a puree and when might be the right time to add it. (Spoiler alert: adding the puree is easy peasy and garners no “reaction” from the marshmallow, and you add it right along with all of the other ingredients). In short, this frosting will now likely be my go-to — and not only cause it’s pink — but because it is spectacularly light and pillowy and marshmallow-y. It’s not too sweet, just slightly berry-ish (although you can increase the fruity flavor if you so desire), super easy to make and is the perfect antidote to a 10 year old’s paint ball bday party.
Chocolate Cupcakes With Strawberry Marshmallow Frosting
Ingredients
For the chocolate birthday cupcakes
- 2 cups cake flour
- 1 tsp baking powder
- 1/2 tsp baking soda
- 1 1/2 tsp salt
- 2 3/4 cups dark brown sugar packed
- 1 cup sour cream
- 1/4 cup heavy cream
- 3 yolks
- 2 large eggs
- 1 Tbsp vanilla paste or extract
- 1 oz unsweetened chocolate
- 1 scant Tbsp espresso powder
- 1 1/4 cups Dutch-process cocoa powder plus 1 tbsp black cocoa powder, if you have it, regular cocoa powder, if you do not
- 1/4 cup oil
- 1 cup boiling water
- 1 stick/8 Tbsp unsalted butter melted and warm
For the strawberry marshmallow frosting
- 2 cups strawberries
- 5 egg whites
- 1/4 tsp cream of tartar
- 1/2 tsp lemon juice
- 1 1/4 cup sugar
- 1/2 cup corn syrup
- 1/8 tsp salt
Instructions
For the chocolate cupcakes
- Preheat the oven to 350 degrees. Line three 12 cup muffin pans with paper liners. Set aside.
- Sift the flour, baking powder, baking soda and salt together into the bowl of a stand mixer and then briefly whisk the mixture to ensure the leavening is incorporated. Add the sugar and place the bowl on the stand mixer fitted with the paddle attachment, and mix on low speed while preparing the rest of the batter.
- In a medium-sized bowl, whisk together the sour cream, heavy cream, yolks, eggs, and paste and set aside.
- In another medium-sized bowl, add the chocolate, espresso powder, cocoa powder, oil, and boiling water to the melted butter. Whisk vigorously until the chocolate melts and the mixture is smooth. The butter may separate from the chocolate a bit once the water is added. Do not worry. After the chocolate mixture is added to the rest of the batter it will all come together.
- Keeping the mixer on low speed, slowly add the sour cream mixture to the dry mixture in the bowl. Once added, stop the mixer and scrape down the bowl with a rubber spatula. Now slowly add the chocolate mixture. Once added, stop the mixer and scrape the bowl with a rubber spatula again, making sure to scrape up from the bottom of the bowl to ensure the chocolate is thoroughly integrated with the rest of the batter. Mix on low speed for an additional 15 seconds and remove the bowl from the mixer. Mix once by hand with a rubber spatula to ensure complete incorporation.
- Use an ice cream scoop to fill each liner 2/3 of the way full. Place one tray at a time in the middle rack of the oven and bake for about 20 to 22 minutes, rotating the pan every 7 minutes. Begin checking for doneness at about 18 minutes (no one likes over-baked cake). The cupcakes are done when a cake tester comes out with a few moist crumbs. Repeat with the remaining two pans.
- Let the cupcakes cool in the pan for about 10 minutes before removing them to a cooling rack. Let them cool until room temperature. While the cupcakes cool, make the frosting.
For the strawberry marshmallow frosting
- Wash and hull the berries and place in a food processor fitted with the metal blade. Process the berries until pureed. Place a sieve over a medium sized bowl and pour the puree into the sieve. Using a rubber spatula, press the puree through the sieve (to remove the seeds).
- In a large heat-proof bowl, combine the whites, cream of tartar, lemon juice, sugar, corn syrup, salt and 1/2 cup of the puree. Whisk the ingredients together and place over a double boiler (place a large pot with an inch or two of water on a medium flame and nestle the bowl of ingredients in the pot, making sure that the bottom of the bowl is suspended over the water and not touching it).
- Using a handheld mixer, on high speed, beat the ingredients in the bowl together until they are miraculously transformed into marshmallow-y loveliness, about 7 or so minutes. Add up to an additional 1/4 cup of puree (or more — I used 3/4 cup, but might add even more next time) if the frosting is not strawberry enough for you. You may also add a bit more lemon juice, 1/2 tsp at a time, as the juice will give the strawberry flavor more depth and will help make it pop. Use the frosting immediately.
- Decorate by placing a small fresh strawberry in the center of each frosted cup.
Notes