Cook the fruit. Place the berries, water, sugar, cinnamon, and vanilla into a saucepan over medium high heat. Cook until warmed through and softened.
Mash. Once bubbling, use a potato masher to break up large fruit pieces. The mixture will not be fully smooth, but large berries should be reduced.
Make the slurry. In a small bowl, whisk together the water and cornstarch until smooth.
Thicken. Stir the slurry into the fruit mixture and continue cooking, stirring frequently, until thickened and bubbling.
Strain if desired. For a smoother syrup, strain through a sieve to remove seeds and berry chunks, then let cool slightly.
Serve. Transfer to a container and serve warm over pancakes.
Notes
Smooth syrup option: For a chunk free syrup, strain the fruit mixture before adding the cornstarch slurry, then return the liquid to the pot and continue cooking.
Thickening: Syrup continues to thicken as it cools. For faster thickening, briefly chill while preparing pancakes.
Sweetener swap: Honey may be used in place of sugar for a slightly different flavor.
Storage: Store sealed in the refrigerator for up to 1 week. Mason jars work well for easy pouring and scooping.