Ingredients
Equipment
Method
- Prepare the Cake Pans: Preheat the oven to 350°F (175°C). Grease three 8-inch round cake pans and line their bottoms with parchment paper.
- Combine Dry Ingredients: Whisk the flour, baking powder, baking soda, and salt together in a bowl. Set the mixture aside.
- Cream Butter, Oil, Sugar: Place the softened butter, vegetable oil, and granulated sugar in a large mixing bowl or stand mixer bowl. Beat for about 2 minutes, until the mixture becomes fluffy and noticeably lighter in color. Use the paddle attachment for a stand mixer or a hand mixer.
- Add Eggs: Add the eggs one at a time, mixing each egg completely into the batter before adding the next. Scrape down the sides and bottom of the bowl as needed.
- Add Vanilla: Mix in the vanilla extract until evenly incorporated.
- Begin Alternating Ingredients: Add one-third of the buttermilk and mix on low speed until incorporated. Add one-third of the dry ingredient mixture and mix again on low.
- Finish the Batter: Continue alternating the remaining buttermilk and dry ingredients in thirds, mixing after each addition and finishing with the last portion of the flour mixture. Mix only until combined, then gently fold with a spatula if needed to avoid overmixing.
- Create the Berry-Free Base: Spoon about 1/2 to 1 cup of plain batter into the bottom of each prepared pan, using enough to cover the base with a layer approximately 3/4 inch thick. This initial layer helps keep the blueberries from settling against the bottom of the pans.
- Add Blueberries: Fold the blueberries into the remaining batter just until they are evenly distributed.
- Fill the Pans: Divide the blueberry batter evenly among the three prepared cake pans, spreading it over the plain batter layer.
- Bake the Cake Layers: Bake at 350°F for about 30 minutes, or until a toothpick inserted into the center comes out clean.
- Cool the Layers: Remove the pans from the oven and let the cakes rest for 10 minutes. Turn the layers out onto a cooling rack or plate and allow them to cool completely before assembling.
- Freeze for Later: If the cake will not be assembled the same day, wrap each completely cooled layer in plastic wrap and place the wrapped layers in the freezer until ready to assemble.
Blueberry Jam
- Cook the Blueberries: Place the blueberries, granulated sugar, and lemon juice in a medium saucepan. Cook over medium heat for about 10 minutes, stirring occasionally, until the berries soften. If the mixture begins sticking or drying out, add 1 tablespoon of water or more as needed.
- Prepare the Slurry: Stir the cornstarch and 2 tablespoons of water together in a small bowl until the cornstarch has completely dissolved.
- Thicken the Jam: Once the blueberries are soft and the mixture is thick and syrupy, pour in the dissolved cornstarch while immediately stirring with a spatula. Continue cooking for 2 minutes, stirring, until the mixture thickens.
- Cool the Jam: Remove the blueberry mixture from the heat and transfer it to a bowl. Cover with plastic wrap and let it cool, then refrigerate until needed for assembly.
Blueberry Puree
- Blend the Blueberries: Place 1 cup of blueberries in a blender and blend until smooth. The puree should yield approximately 1/2 cup.
- Reduce the Puree: Transfer the puree to a medium saucepan and cook over medium heat. Bring it to a simmer, stirring frequently.
- Concentrate the Puree: Continue cooking until the puree has reduced to 1/4 cup.
- Cool the Puree: Transfer the reduced puree to a bowl and press plastic wrap directly against its surface to prevent a crust from forming. Let it cool completely. It can also be refrigerated overnight before use.
Blueberry Cream Cheese Frosting
- Beat the Butter: Place the butter in a mixer bowl and beat for 30 seconds.
- Add Cream Cheese: Add the cream cheese and beat on medium speed for another 30 seconds.
- Add Half the Sugar: Add half of the powdered sugar and mix on low until incorporated. Increase the speed to medium and beat for a few seconds.
- Add Blueberry Puree: Mix in the 1/4 cup blueberry puree on low speed until evenly combined.
- Finish the Frosting: Add the remaining powdered sugar and mix on low until incorporated. Increase the speed to medium-high and beat for 1 minute, until the frosting is fluffy.
- Adjust Consistency: If the frosting is too runny, add a little more powdered sugar until it reaches a thicker consistency.
Assemble the Cake
- Position the First Layer: Place one completely cooled cake layer on a cake plate or cake stand.
- Spread Frosting: Apply a thin layer of blueberry cream cheese frosting over the top of the cake layer.
- Pipe the Frosting Border: Transfer some of the frosting to a piping bag fitted with a large round tip. Pipe a ring around the outer edge of the cake layer.
- Add the Jam: Spread blueberry jam inside the frosting ring, keeping the filling contained within the border.
- Stack the Second Layer: Place the second cake layer on top of the filling.
- Repeat the Filling: Spread another thin layer of frosting over the second layer, pipe a frosting ring around its edge, and fill the center with blueberry jam.
- Add the Final Layer: Place the third cake layer on top.
- Apply the Crumb Coat: Spread a thin layer of frosting over the top and sides of the assembled cake. Smooth it with an offset spatula or cake scraper to seal in the crumbs.
- Chill the Cake: Refrigerate the crumb-coated cake for about 20 to 30 minutes, until the frosting layer has chilled.
- Apply the Final Frosting: Remove the chilled cake from the refrigerator and spread the remaining frosting generously over the top and sides.
- Smooth the Sides: Hold a cake scraper steadily against the side of the cake while rotating the cake turntable to create a smooth finish.
- Smooth the Top: Use an offset spatula to smooth the top, gently drawing the spatula over the edges toward you.
- Decorate the Cake: Finish the cake with fresh blueberries and mint leaves, if desired.
Storage
- Refrigerate Leftovers: Store leftover cake slices in the refrigerator in an airtight container.
- Freeze the Cake: To freeze the cake, wrap it in plastic wrap and place it in an airtight container. Remove the fresh blueberries before freezing.
Notes
- Use room-temperature eggs and buttermilk for a smoother, more evenly mixed cake batter.
- The butter should be softened before preparing the batter; the source notes that it is ideally around 72°F.
- Fresh or frozen blueberries can be used throughout the recipe, except for the decorative blueberries.
- If preferred, store-bought blueberry jam can replace the homemade blueberry jam.
- For a buttermilk substitute, add 1 teaspoon of vinegar to regular milk, let it stand for 2 minutes, then use it in the recipe.
- The plain layer of batter placed at the bottom of each pan helps prevent the blueberries from sinking.
- Avoid overmixing once the flour has been added. Finish gently with a spatula if needed.
- The blueberry puree can be prepared ahead and refrigerated overnight.
- Allow the cake layers to cool completely before beginning assembly.
- Chill the crumb-coated cake for 20 to 30 minutes before applying the final frosting layer.