1. Preheat the oven to 350°F (180°C). Line a springform tin (8 inches/20cm) with baking parchment and set aside. Defrost the frozen blueberries.

 

2. Add the eggs, sugar, salt, and vanilla extract to a large bowl and mix on high speed until light and fluffy for about 4-5 minutes. Mix the flour with baking powder, sift into the bowl and fold in. Fill the batter into the prepared baking tin, smooth out the top and bake for 23-25 minutes or until a toothpick inserted into the center comes out clean. Take out of the oven and run a knife immediately around the cake to loosen it from the baking tin, remove from the tin and place with the baking parchment on a wire rack to cool down.

 

3. Remove the baking parchment from the cake and place it inside an adjustable cake ring on a serving plate. Pull the ring together so it sits tight around the cake layer. Place the waffle rolls along that cake ring on top of the cake layer to form a barrier to hold the filling later on. Try to place the waffle rolls very close to each other so no filling can get through. Set aside.

 

4. For the filling add the gelatin leaves to a bowl with cold water and let soak for 6-8 minutes. Wash and dry the strawberries and remove the green parts. Puree together with the sugar. If you want the filling of the cake to be more vibrant, add the red beet root powder and mix in (optional). Add the soaked gelatin leaves with 3-4 tablespoons of the puree to a small saucepan and heat up gently until the gelatin has dissolved. Remove from the heat and set aside. Mix the remaining strawberry puree with the mascarpone and then mix with the dissolved gelatin mixture. Whisk the heavy cream until stiff peaks form, add to the bowl with the strawberry mix and fold in. Add the defrosted blueberries and fold in. Pour into the prepared tin and smooth out the top. Place in the fridge for at least 3 hours. Decorate with some strawberries and blueberries before serving.