In a medium saucepan set over medium heat, combine 2 cups blueberries, maple syrup, water, lemon juice, and cinnamon. Cook for 10 minutes, stirring occasionally. Reduce heat to medium-low, add the remainder of the blueberries, and cook for 5 to 8 more minutes (or until compote reaches your desired consistency), stirring frequently. Remove from heat and stir in vanilla. Serve warm.
The frozen blueberries do not need to be thawed. You may use fresh blueberries if you wish, but you will probably want to reduce the total cooking time by a few minutes.
If your berries are particularly sour or sweet, you may increase or decrease the maple syrup.
This compote is not necessarily thick...when it's finished cooking, it's a mixture of stewed berries with a bit of syrup.
This recipe only makes ½ cup, but it's very concentrated, so a little bit goes a long way.