Blueberry Cake Layer:

Prep: Preheat the oven to 350°F (175°C). Line the bottom of a 9″ springform pan with parchment paper and clamp it in between the bottom plate and the ring.

Mix the Batter: In a large bowl, whisk together cake flour, baking powder, baking soda, and salt. Add sugar, milk, oil, egg, and vanilla extract. Whisk until smooth.

Bake the Cake: Pour the batter into the springform pan and scatter a handful of blueberries over the top (optional). Bake for 15-20 minutes, or until lightly browned and a toothpick inserted in the center comes out mostly clean. Let cool completely on a wire rack.

Prep the Cake and Pan: Once cooled, run an offset spatula around the edges to release the cake. If the cake is domed, remove it from the pan, level it with a serrated knife, and return it to the pan. Line the sides of the pan with acetate or parchment paper.

Blueberry Mousse:

Bloom Gelatine: In a small bowl, sprinkle gelatine powder over cold water and let it sit for 5 minutes to bloom.

Puree Blueberries: Blend the blueberries in a blender until smooth.

Add Gelatine: Heat the bloomed gelatine in the microwave in 10-second increments until dissolved into a clear liquid. Add it to the blueberry puree and blend for 30 seconds.

Whip Cream: In a large mixing bowl, whip the whipping cream and powdered sugar to firm peaks.

Fold in Blueberry Puree: Gently fold the blueberry-gelatine mixture into the whipped cream until smooth and well-combined.

Fill the Pan: Pour the mousse over the cooled cake in the springform pan. Gently jiggle the pan to settle the mousse or smooth with an offset spatula.

Chill:

Cover and refrigerate the cake for at least 6 hours, preferably overnight, until the mousse is set.

Toppings:

Whip Cream: In a medium bowl, whip the whipping cream, powdered sugar, and vanilla extract until firm peaks form. Transfer to a piping bag fitted with a piping tip.

Decorate: Release the cake from the springform pan and remove the acetate sheet. Pipe the whipped cream on top of the mousse layer. Garnish with fresh berries.