"I often make crêpes with a blueberry filling and wanted a quick recipe for making blueberry preserves suitable for one or two serving sizes. It will store well for weeks in the refrigerator but would not be suitable for storage like you might find for canned jellies and preserves since none of that labor/cost is involved. This recipe relies on the natural sweetness of fresh blueberries and the grape juice plus a small amount of Karo syrup to assist with the texture."
Put half of the blueberries into a bowl and crush them using a potato masher or similar
In a medium-sized saucepan over medium-high heat start reducing the grape juice, stirring with a wooden spoon. It should start to behave more like a syrup.
Lower the temperature to medium, continuing to stir
Add the lemon juice, continuing to stir
Stir in the Karo syrup and the crushed blueberries
Continue cooking/stirring until the mixture gets sticky like what you'd expect in a preserve
Add the remaining blueberries and stir until all are coated, removing from heat and putting into a glass container/jar (refrigerating) or adding immediately to your waffles/pancakes/crêpes (served warm).