While the cake bakes, heat up the blueberries in a small saucepan. Once it starts to slightly boil, take it down to a low heat and let the blueberries simmer under a lid for 8 minutes. After the 8 minutes, take the lid off and let it continue to simmer without the lid for 5 minutes. Stir occasionally. Then take it off the heat and blend it in a blender until smooth. Let it cool down on your kitchen counter or in the fridge until room temperature.
150 g frozen wild blueberries
Once the cake has cooled down, make the frosting.
TIP: If you live in Europe, place your cream cheese between a few pieces of paper towels to remove any excess water.
100 g full-fat cream cheese
Sift the powdered sugar.
360 g powdered sugar
In your stand mixer, using the paddle attachment, start by creaming the butter for 5 minutes on high speed. Scrape down the sides of the bowl and give it another mix for 2 minutes.
200 g butter
Add the cream cheese, vanilla bean paste, 2 tablespoon of the blueberry purée, saving the rest of the blueberry purée for later, and cream it together with the butter for 1 minute.
½ teaspoon vanilla bean paste
Scrape down the sides of the bowl and on low speed, mix the sifted powdered sugar in 2 parts, letting the powdered sugar mix in with butter and cream cheese before adding the next part. Scrape down the sides of the bowl and give it a final mix for 2 minutes.
Take the bowl off the stand mixer and with a spatula or wooden spoon, beat it well by hand to make sure to remove the air bubbles in the buttercream.
TIP: It is a softer buttercream. If too soft, place it in the fridge for 5-10 minutes. Then give it a good whisk before adding it to the cake.
Finally add the buttercream to the chocolate cake and with an offset spatula spread it out evenly. Dollop on the remaining blueberry purée and swirl it in.