I could never resist tasting it when it was still hot - still can't, as my burnt tongue will testify. Half the blueberries pop, yielding a clear, thin, purple syrup. The rest cook just to the point of bursting, and they're soft and sweet. As the sauce cools, it thickens. Depending on how long you cook it and how much cornstarch you use, it can be totally runny or as thick as pie filling. (Come to think of it, this would be a great pie filling!) I prefer to eat it with a spoon, straight out of the fridge, but it also is an excellent topping for waffles, pancakes, or vanilla ice cream.
The amounts below are approximated, and I'd encourage you to tweak it to your tastes. Sweeter berries won't need as much sugar; less water will make a thicker sauce.
Fresh Blueberry Sauce
Makes about 2 1/2 cups
2 pints fresh blueberries
2/3 cup water
1/4 to 1/2 cup sugar (start with 1/4 cup and add more if needed)
1/2 tablespoon cornstarch
dash of cinnamon
1 tablespoon lemon juice
Rinse the blueberries and remove any stems. In a medium saucepan, stir together the water, sugar, cornstarch, and cinnamon. Add the blueberries and stir gently. Cook over medium heat, stirring regularly. Add the lemon juice. Continue cooking until the sauce is clear and thickened and about half the blueberries have popped, about 10 minutes. Let cool enough to taste, and add more lemon juice or sugar if needed. Cool completely, then place in a jar and refrigerate.