1. Preheat the oven to 180°C (350°F). Lightly grease a springform tin with a funnel base* (26 cm), dust with some flour, and set aside.

2. Combine flour, cornstarch, baking powder, baking soda, and salt and set aside. Mix the milk with the lemon juice in a small bowl and let it thicken/curdle for 5-8 minutes. Wash and drain the blueberries.

3. Mix the butter with sugar and lemon zest in a large bowl on high speed until very light and fluffy. Add the eggs one at a time and stir well after each addition. Add the vanilla extract and stir in. Next, add the flour mixture and the curdled milk in three batches to the bowl, stirring only briefly after each addition. Do not overmix the cake batter!

4. Mix the still-wet blueberries with the teaspoon of flour and fold into the batter – the flour will help to prevent the blueberries from sinking to the bottom. Pour the batter into the prepared baking tin, smooth out the top, and bake for about 55-65 minutes – or until a toothpick inserted into the cake comes out clean. The top of the cake should have a nice golden color. In case it gets too dark, cover everything with aluminum foil or baking parchment and continue baking. The baking times can vary greatly depending on the oven and baking tin used, so be careful! Remove the cake from the oven and let it cool inside the baking tin for about 20 minutes, then carefully remove it and let it cool completely on a wire rack.

5. For the buttercream, add the egg whites, sugar, and salt to a large bowl and place it on top of a saucepan with simmering water. Mix until the mixture reaches a temperature of 71°C (160°F). Once the temperature has been reached, remove the bowl from the saucepan. Add the egg mixture to the bowl of a kitchen machine and mix for about 5 minutes – the egg whites should be stiff and shiny, the temperature of the meringue should have come down to room temperature. Gradually add the butter in small pieces and mix well after each addition. Add the vanilla extract and confectioners’ sugar and mix slowly at first, then at high speed for about 5 minutes. The result should be a very silky and creamy buttercream.

6. Add the buttercream for the flowers into several bowls and mix in a few drops of food coloring until the desired color intensity is achieved (you only need a small amount of green buttercream). Fill the individual colors into piping bags with different flower petal nozzles*. Pipe buttercream flowers onto pieces of paper using the different colors, and then place them in the fridge for about 30 minutes. If you don’t want to go to the trouble of making buttercream flowers, you can just use different sized star nozzles and pipe dots and swirls onto the cake.

7. For the glaze, mix the confectioners’ sugar with lemon juice and blueberry sauce (or blue food coloring). Depending on the thickness of the glaze, add heavy cream and stir until smooth (you want a thick consistency). Glaze the cake with and let it dry for a few minutes, then place the buttercream flowers on top and decorate with more buttercream dots, leaves, and blueberries. Place in the fridge until ready to serve.