• Mix all the batter ingredients in a bowl until the batter is smooth and has no lumps.
• Fill the batter into two 18 centimeter diameter cake tins lined with parchment paper. If you don't have two tins, just bake half first and the other half afterwards in the same tin.
• Bake the cakes for 30 minutes or until a knife comes out clean.
• Combine all the filling ingredients in a pan and cook on a medium heat for 5-10 minutes until the berries are tender and some juice exits the berries. Let it cool.
• Whip the cream. Then add the blueberries and whisk for another short moment until the blueberries are mixed in and the mousse looks purple.

Assembly

• When your cakes are cool, trim them if you like so that they have straight edges and you have something to taste or leave them as they are if you don't mind if the cake doesn't look perfectly straight in the end. The surfaces should however be straight or the layers will slide apart. So cut some of the top off the cakes to make them flat if necessary.
• Place one cake on a plate, evenly drizzle 1 tbsp of lemon juice over the cake. Next spread an approximately 1 centimeter thick layer of the blueberry mousse on the bottom layer. Carefully place the second cake on top. Drizzle that with the other tbsp of lemon juice and top with mousse. To coat the cake all around, rather use too much mousse and scrape it off again after applying since that prevents annoying crumbs from getting in your business.
• If you can wait - place the cake in the fridge for a while to let flavors and stability improve.