Blackberry Cake

Preparation

For the Blackberry Purée

Step 1
Combine lime juice and cornstarch to make a slurry and mix until there are no lumps.

Step 2
Mix the blackberries and salt in a saucepan and use an immersion blender to make the filling smooth.

Step 3
Turn on the heat and cook down the berries. Keep stirring to keep the puree from cooking too quickly on the bottom of the pan.

Step 4
Once the purée has thickened up slightly, remove it from the heat and stir in the lime zest.

Step 5
Transfer the purée to a large bowl to cool to room temperature.

NOTE: You will use about 6 tablespoons of the purée to add to your cake. About ¼ to ½ cup of purée will be for the buttercream. If you choose to strain the seeds out of all of the purée, add a couple of extra ounces of berries to account for the loss in straining.

Store leftover puree in the fridge for up to a week or freeze for 6 months.

For Blackberry Cake

Step 1
Heat oven to 335ºF / 168ºC and prepare two 8″x2″ round cake pans with Cake Goop or another pan release and parchment paper if you prefer.

Step 2
Measure out the buttermilk and place 4 oz in a separate measuring cup. Add the oil to the 4oz of buttermilk and set aside.

Step 3
Add your eggs and lime zest to the remaining milk and gently whisk to combine. Keep the lime juice separate, you will add this at the end.

Step 4
Place the flour, sugar, baking soda, and salt into the bowl of your stand mixer with the paddle attachment. Liz uses a Bosch universal plus mixer but you can use a hand mixer, just mix for longer.

Step 5
Turn the mixer onto the slowest speed. Slowly add chunks of your softened butter until it is all added. Let everything mix until it looks like coarse sand. Add your milk/oil mixture all at once to the flour mixture. Mix on medium for 1 full minute to develop the structure. Don’t worry, this will not over-mix the cake. Because it is AP flour you do not need to mix as long as cake flour (more gluten, less time needed).

Step 6
Scrape the bowl. This is an important step. If you skip it, you will have hard lumps of flour and unmixed ingredients in your batter. If you do it later, they will not mix in fully.

Step 7
Slowly add in the rest of your milk/eggs/zest ingredients in 3 parts. Next, pour in the lime juice with the last addition of liquid, stopping to scrape the bowl one more time halfway through. Your batter should be thick and not too runny.

Step 8
Fill your pans ½ full with cake batter.

Step 9
Spoon about 2 tablespoons of room-temperature puree over the batter. Use a small spatula or knife to gently fold the purée in to create a swirl effect into the batter.

Step 10
Toss fresh or frozen blackberries lightly in 2 tablespoons of flour. Add the floured blackberries to the top of the batter. Do not push them down as their weight will cause them to sink anyway as the cake heats up.

Step 11
Place the cakes in the preheated oven. Bake for 30 minutes for 6″ and 8″ cakes and 35 minutes for 9″ and larger cakes and then checking for doneness. If the cakes are still really jiggly, add another 5 minutes. Check every 2 minutes after that until they look close to done and then check every 1 minute. Cakes are done when a toothpick inserted in the center comes out with a few crumbs.

Step 12
After the cakes have cooled for 10 minutes or the pans are cool enough to touch, place a wire rack on top and flip the cakes over to remove them from the pans. Let them rest on a cooling rack to cool completely, or wrap in plastic wrap and chill in the freezer.

For the Blackberry Buttercream

Step 1
Strain out the seeds of the blackberry purée. This is optional but it will make a smoother texture when scraping the sides.

Step 2
Place the egg whites and powdered sugar in the bowl of your stand mixer with the whisk attachment and whip on high speed for 3-5 minutes. An electric mixer and a large mixing bowl will also work, just mix for longer.

Step 3
Add the softened butter in small chunks then vanilla and salt. Whip on high until light and fluffy and white, about 8 to 10 minutes.

Step 4
Add about ½ cup of the blackberry purée to the buttercream and continue to whip until combined.

Step 5
Mix in about 1-2 drops of pink food coloring to enhance the color if you choose.

Step 6
Optional: Switch to the paddle attachment and mix on low for 15-20 minutes until all air bubbles are gone.

Note: Store it in an airtight container for up to a week in the refrigerator or for 3 months in the freezer.

For the Blackberry Gummies

Step 1
Defrost your berries and separate the fruit from the blackberry juice. You can use the solids to make fruit filling or freeze to use later.

Step 2
Combine the juice with the powdered gelatin and allow to absorb for 10 minutes.

Step 3
Combine the sugar and the water in a large saucepan and bring to a boil. Once the steam begins to disappear and the mixture begins to look thick and bubbly (around 145ºF) turn off the heat.

Step 4
Add in the gelatin and blackberry juice mixture in chunks, the glucose or corn syrup, citric acid and the candy flavoring.

Step 5
Mix until fully melted.

Step 6
Transfer the mixture to a squeeze bottle and pipe into your desired molds.

Step 7
Refrigerate for a minimum of 4 hours before unmolding.

For the Cake Decorating/Assembly

Step 1
Once your cakes are chilled, trim off the dome and brown edges of the cake. This is optional but makes for pretty slices.

Step 2
Place your first cake layer onto a board.

Step 3
Spread on about ¼” of your blackberry buttercream.

Step 4
Layer some fresh blackberries into the buttercream.

Step 5
Spread some more buttercream on top of the blackberries and then add your next layer of cake. Repeat the process with layer two and then add your final layer of cake on top.

Step 6
Cover the whole cake in a thin layer of buttercream. This is the crumb coat.

Step 7
Place the cake into the fridge or freezer for 20 minutes to set the buttercream layer.

Step 8
Apply your final coat of buttercream and use a bench scraper and offset spatula to make it nice and smooth.

Step 9
Decorate the top of the cake with more dollops of buttercream, Blackberry Gummies (or fresh blackberries) and some lime zest.

Step 10
Chill, slice and enjoy!