In a small pot, combine blueberries, 1/2 cup water, and sugar. Heat on medium-high until it starts to boil and blueberries begin to break. Stir occasionally.
Whisk 2 tablespoons of water and cornstarch in a small bowl until smooth. Add to the blueberries, bring to a rolling boil, then simmer for 3–4 minutes until the syrup thickens. (If the sauce is too thick, thin with 1 tablespoon of water at a time.)
Optional Blend:If you want a completely smooth syrup, use an immersion blender to blend or carefully transfer to a blender and process until smooth.
Remove from heat and stir in vanilla extract or lemon juice (but not both). Serve warm over pancakes, French toast, or crepes.
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Notes
Note 1: Taste the blueberries first; add extra sugar if tart, and use less if sweet. Adjust as needed after cooking.Nutrition Note: Nutritional information is based on 1/3-cup servings.Storage: Allow syrup to cool, then store in an airtight container in the fridge for up to 2 weeks. Freeze for up to 3 months. Thaw in the fridge and reheat gently before use.