Line your 8x8 cake pan with tin foil or baking parchment paper. Cover the bottom with waffles. Make sure there are no empty spaces in between them. Now scatter fresh blueberries over the waffles.
Melt white chocolate with 1 cup whipping cream over a pot of simmering water. Remove from the heat and let cool slightly before stirring in gelatin sheets that have been soaked in water (follow the package instructions). Let it cool down.
Whip the rest of the cream and fold it into the chocolate mixture. Pour it into the cake pan and refrigerate for 2 hours.
Before serving make the blueberry topping by simmering blueberries, sugar and freshly squeezed lemon juice in a small sauce pan.
When the berries have softened and the sugar has melted add cornstarch that you have dissolved in 2 tablespoons of water. Cook for a further 1-2 minutes before turning off the heat.
Slice the cake, pour the blueberry sauce over each slice and serve!