Fresh, Filled Blueberry Shortbread Crumble Cake

Mandy Merriman shares how to make a blueberry shortbread crumble cake.

Find more cake recipes at www.bakingwithblondie.com, or on Instagram, @bakingwithblondie. Find Mandy’s cookbook here.

Blueberry Shortbread Crumble Cake 

INGREDIENTS

Blueberry Cake with Shortbread Crust

• 24 shortbread cookies
• 4 Tablespoons unsalted butter, melted
• ½ cup buttermilk (room temperature)
• ½ cup sour cream (room temperature)
• 3 eggs + 1 egg white (room temperature)
• ⅓ cup vegetable oil
• 1 Tablespoon pure vanilla
• ½ cup fresh blueberries, pureed
• 1 Tablespoon blueberry emulsion
• 1 box white cake mix

Blueberry Filling

• 1 cup fresh blueberries
• ¼ cup + 1 Tablespoon sugar
• 3 Tablespoons lemon juice
• 2 teaspoons cornstarch

Blueberry Buttercream 

• 1 ½ cup unsalted butter
• Pinch of salt
• 1 Tablespoon vanilla
• 1 Tablespoon blueberry emulsion
• ¼ cup heavy cream
• 8 cups powdered sugar

Shortbread Crumble

• ⅔ cup reserved prepared shortbread crumble (see recipe with shortbread crust on cake) 

Extras

• Fresh Blueberries
• Blueberry plant leaves, or small mint leaves (leaves cleaned before decorating and also removed before serving)

METHOD

For the Blueberry Cake with Shortbread Crust

1. Preheat the oven to 325 degrees, then prep three 6” cake rounds with a swipe of shortening and dust of flour to prevent sticking. Set aside.
2. In a food processor, pulse together the shortbread cookies and melted butter until a fine crust forms. Reserve ⅔ cup of the shortbread crumble and set aside.
3. Split the rest of the crust evenly between the three prepared cake rounds and press down to firm with the bottom of a glass or flat measuring cup. Set aside.
4. In a large mixing bowl, hand whisk together the buttermilk, sour cream, eggs, oil, vanilla, blueberry puree and blueberry emulsion until thoroughly combined. Sift in the cake mix and whisk until just combined. Do not overmix. Split the batter evenly between the prepared cake rounds.
5. Bake for 32-35 minutes until the center is baked through. Remove cake rounds from the oven,  then let the cakes cool in the pan for a minute before flipping them out onto a wire rack to cool completely. Wrap and chill cakes flat before assembly.

For the Blueberry Filling

1. In a small saucepan over medium heat, stir together the blueberries, lemon juice, and sugar until thick and bubbly, about 5 minutes. Sift in the cornstarch and stir until thickened. Place the filling in a bowl, cover, and refrigerate until thickened and cooled completely. 

For the Blueberry Buttercream

1. In the bowl of a stand mixer fitted with a paddle attachment, whip up the butter until it’s light and fluffy. Add in the salt, vanilla, blueberry emulsion, and heavy cream. Whip up to combine and then scrape down the sides with a spatula.
2. With the stand mixer on low speed, add in the powdered sugar about a half cup at a time. It will be thick. Add in a little more heavy cream to thin it out if needed (1 Tablespoon at a time), and then flip the mixer on high speed for 2 minutes to lighten the color and texture of the buttercream.

For the Shortbread Crumble

1. Preheat the oven to 350 degrees. Spread out the reserved crumble on a parchment-paper lined cookie sheet. Bake for 7-10 minutes until toasted golden. Set aside to cool completely before adding it to the cake. 

Assembly

1. Place a cardboard cake round on a cake turntable. Spread on a little bit of buttercream in the center of the round and spread it out with an angled icing spatula. Place down the first chilled cake layer in the center. Add on a thin layer of buttercream; spread it thin with an angled icing spatula. Pipe a buttercream dam around the outside rim of the frosted cake layer, add in about ½ cup of the blueberry filling.
2. Place the next cake layer on top, then repeat – making sure to line the layers up evenly. After adding on the top cake layer, crumb coat the cake by spreading the buttercream in a thin layer around the entire cake. Freeze for 2 minutes to set the buttercream.
3. Using a wooden spoon, hand-beat out any air bubbles in the remaining buttercream. Spread on a final layer of buttercream around the entire cake, using a cake scraper for smooth sides and clean edges. Leave the top edge unfinished for a rustic look.
4. Press on groups of three blueberries into the buttercream and one leaf per trio. Add the baked crumble to the top.