Adapted from the amazing NotCharlesManson's Strawberry Shortcake Bar. All I did was replace the strawberries with blueberries. I think it turned out really good. I did have to play around a bit with the blueberries, but I think I finally came up with the right mix and percentages.
The sweetener, in my case Pyure Stevia, can obviously be adjusted or omitted according to taste.
I gave it 5 stars but all the credit goes to NotCharlesManson. With his base, I'm fairly sure that replacing the strawberries with pretty much anything would still be great,