In a small saucepan, combine all the ingredients over medium-low heat. Stir until the blueberries have begun to release their juice and the mixture is soup.
Increase the heat to medium-high and bring to a low simmer. Stir frequently as the mixture thickens.
Cook until the blueberry topping has reached your desired thickness. If the mixture becomes too thick, add water a couple tablespoons at a time and combine well.
Notes
This recipe can be easily halved to make less topping, or doubled to make more.
Try adding citrus zest or nuts for different flavor, or try strawberries, raspberries or blackberries.