I saw it from across the internet. It was a Pinterest pin so full of win; a cake so lovely that I knew it must be mine or I would never be complete. That was my first impression of Sweetapolita’s Vanilla Blackberry-Mascarpone Cake for Two. And, as it turns out, it was destined to become my birthday cake. Oh, it’s not exactly the same cake: I made an insanely moist chocolate buttermilk cake instead of the original yellow sponge cake she used, and the frosting is vanilla swiss meringue, because it happens to be my favorite. But the fresh blackberries and whipped mascarpone filling are still very much represented, and her watercolor frosting is so pretty that I just had to try doing it myself.
Now, I’m more of a cake eater than a cake decorator, but I can make a pretty good looking cake when I set my mind to it – with one caveat: I’m horrible at abstract decorations. Ask me for basket weave or ruffles, and I can do that all day. However, I must admit that unstructured designs (like free-form watercolor swirls) make me nervous. How do I know when it’s done? I don’t. So I keep fussing, and fussing, until I fuss too much and end up ruining it. She made it look easy, though. So after watching the tutorial a half dozen times, and pouring myself a stiff glass of liquid courage, I got to work.
And…. It was pretty! Not perfect, of course, but that’s sort of the bright side of this kind of technique. It’s not supposed to be perfect. And that’s what makes it awesome.
Oh, and did I mention that it totally tastes like wedding cake? The filling is so creamy and light, and the burst of fresh blackberry is so delicious with the chocolate cake and silky frosting. I would love to try this again with a different fruit, because I found all the seeds in the berries to be a little distracting, but that’s really the only complaint.
Just look at this unspoiled loveliness. You know what I’m going to do? Spoil the crap out of it. With my mouth.
I’m not going to give decorating instructions, because I just followed Sweetapolita’s instructions for that part, and she already has a great video with step-by-step instructions for the frosting. While my cake doesn’t look as effortlessly pretty as hers, I did have a blast making it, and it tasted amazing.
Chocolate Blackberry-Mascarpone Cake
Chocolate Buttermilk Cake
1 cup white sugar
1 cup cake flour
1/4 cup plus 2 tbsp cocoa powder
3/4 tsp baking soda
3/4 tsp baking powder
1/2 tsp salt
1/2 cup butter, softened but still cool
1/2 cup buttermilk
1 tsp vanilla extract
1/2 cup hot coffee
Vanilla Swiss Meringue Frosting
5 egg whites
1¼ cup sugar
¼ tsp cream of tartar (heaping ¼ teaspoon)
2½ cups unsalted butter (5 sticks, softened, cut into 1 tbsp pieces)
1 tbsp vanilla
1 cup fresh blackberries
1 tbsp blackberry jam
Squeeze of fresh lemon, about a tsp
4 oz mascarpone, room temperature
3/4 cup heavy cream
1 tsp vanilla
1/4 cup powdered sugar
What else you’ll need:
2 or 3 stiff pieces of cardboard or card stock, trimmed to the the approximate size of your cake
Food dye and sprinkles, if using, for decoration
- For the cake: Preheat the oven to 350°F. Grease and flour a 10×10 baking pan, and line with parchment paper, ensuring that the paper comes up and over the sides of the pan. You can criss-cross two wide strips of parchment paper for this.
- In the bowl of a standing mixer fitted with the paddle attachment, add the first six ingredients and set the mixer to stir, stirring until the dry ingredients are well combined. With the mixer still on stir, add the butter pieces one at a time until they’ve all been added. Bump the speed up slightly to low, and mix until the mixture looks like wet sand, and the biggest piece of butter is no larger than a pea.
- Meanwhile, combine the egg, buttermilk, and vanilla in a small bowl. Reduce the mixer speed to low, and drizzle in the wet mixture until just incorporated. Increase the speed to medium-high, and beat the batter until light and fluffy, about a minute. Scrape down the sides of the bowl, and continue beating another 10 to 15 seconds. Reduce the speed to stir and drizzle in the hot coffee. Continue stirring until the mixture is fully combined, stopping once or twice to scrape the sides and bottom of the bowl. The batter will be a bit thin, but that’s okay.
- Pour the batter into the prepared pan and bake for 30 minutes, or until the top springs back with lightly touched. Allow to cool for 10 to 15 minutes, then turn out onto a wire rack and cool completely.
- For the filling: warm the jam slightly in the microwave until just runny. Toss the jam with the fresh berries, mashing the berries lightly to release their juices. Stir in the lemon juice, and set aside.
- In a small bowl, beat the mascarpone until smooth. If your mascarpone is still too cold, it may not smooth out right away. If this happens, immerse the bowl in a dish of hot tap water and continue mixing until it smooths out. Then use a separate bowl to whip the cream until it reaches soft peaks. Add the powdered sugar and vanilla to the cream, and continue to beat until the cream holds stiff peaks. Fold the mascarpone thoroughly into the whipped cream, and refrigerate until ready to use.
- For the frosting: In a metal bowl (I use the metal bowl of my mixer, otherwise use a double boiler), whisk together the egg whites, sugar, and cream of tartar. Warm the mixture gently over a pot of simmering water, stirring occasionally with a wire whisk until the sugar has dissolved completely and the mixture reaches 160°F. Transfer the syrup to a standing mixer fitted with the whisk attachment, and whip on high until thick and white, about 5 minutes. It will resemble melted marshmallow.
- Remove the whisk attachment, tapping the whisk firmly against the side of the bowl to shake off the whipped syrup (if you use your fingers you’ll get sweet gooeyness all over yourself, mark my words). Attach the paddle attachment and set the speed on the mixer to medium-high. Add the butter one piece at a time, until it has all been added to the bowl. Continue to beat until the frosting is smooth and creamy. If your butter is too cold, the mixture may appear curdled. Simply crank up the speed and beat until the mixture smooths out.
- To assemble the cake: level the cake, and then divide the square into 4 equal sized pieces. Do a preliminary stack of the cut cake pieces, to get a feel for how the pieces will best fit together to form squared sides. Trim if necessary.
- When you’re ready to assemble, pipe icing along the perimeter of the bottom piece of cake, to form a dam. Fill the dam with a generous scoop of the mascarpone cream, then top that with some of the berries and their juices. Top that with the next slice of cake, turning the piece as needed to keep the edges aligned with the bottom piece. Repeat piping and filling this layer. Repeat the layering process until you have filled three layers. Top the cake with the last slice, and inspect the cake for “layer integrity” – if any of the filling appears to be trying to make a break for it, pipe a little more icing at that spot to mortar it back into place. Place the stiff card stock on the sides of the cake, to keep the sides straight, and wrap the cake firmly (but gently!) with plastic wrap to hold everything in place. Chill for at least an hour.
- Once the cake has fully chilled, give it a thin crumb coat, and refrigerate again (without the cardboard and plastic wrap) until the frosting has firmed.
- Color the remaining frosting with whatever colors make your eye sparkle, and frost the cake, topping with sprinkles as desired.
- Serve the cake at room temperature for maximum creaminess of the frosting and filling.