Wash and soak the blueberries in water beforehand. You can even crush a few berries to color the water.
Grind the chocolate or cocoa biscuits in a blender or food processor or simply crush them very well. Mix them gradually with the melted butter, 1/2 of the rum essence and stir until the mixture becomes homogeneous. Spread it in the bottom of an appropriate cake form, making an even layer.
Put the gelatin to swell in as much water as needed, while also using the one from the blueberries.
Beat the cream cheese, sugar, sour cream, cottage cheese, 1/2 of the remaining rum essence, until you get smooth mixture, you can even add a little milk. Melt the gelatin and once it cools, add it to the cream, while gently stirring the entire time.
Pour the milk mixture over the layer and drop some dried berries on top. Top with a few tablespoons of blueberry jam and using a fork or knife, make a few waves for decoration. Carefully place the blueberry cheesecake in the refrigerator overnight to set.
Then sprinkle with more blueberries on top and serve it.