To make the filling, combine all ingredients in a bowl and mix well.
Set aside.
To make the crust, grease a 21 cm (8 inch) springform pan (or round pan with removable bottom) with fat. Preheat oven to 180°C. (350°C)
Combine oats, flour, cocoa powder, sugar, and salt.
Mix well.
Add soy milk and coconut oil and knead until combined.
Press the dough into the pan and bake for 10 minutes.
Meanwhile prepare the topping: place blueberries in a small pan and cook until they start to release their juice.
Mix water and agar and add to blueberries while stirring. Cook for 2 minutes. Set aside.
Remove crust from oven and spread filling on top.
Pour topping over the cake and bake for another 40-45 minutes.
Let cool completely (preferably in the fridge) before serving.