Measure the blueberries, sugar, and water. If using frozen blueberries, do not thaw; they may be added frozen. Zest the lemon, then squeeze to get 2 tablespoons of juice. In a small bowl mix the cornstarch with 1 tablespoon cold water to form a slurry (set aside).

Combine and bring to simmer

In a medium saucepan over medium heat combine the blueberries, granulated sugar, and 1 cup water. Stir briefly to distribute the sugar. Heat until the mixture comes to a gentle simmer and the blueberries begin to burst, about 6–8 minutes, stirring occasionally to prevent sticking.

Add flavorings

Once simmering and some berries have burst, add the lemon juice, lemon zest, ground cinnamon, vanilla extract, and a pinch of salt. Stir to combine and continue to simmer gently for 3–5 minutes to deepen flavors.

Adjust thickness (optional)

If you prefer a thicker compote, stir the cornstarch slurry again and slowly whisk it into the simmering blueberry mixture. Cook for 1–2 minutes until the compote thickens and becomes glossy. If not using cornstarch, simmer an additional 3–5 minutes to reduce liquid.

Finish

Remove the pan from heat and stir in the tablespoon of unsalted butter until melted and incorporated — this mellows the acidity and gives a silky finish. Taste and adjust: add up to 1 additional tablespoon sugar if you want it sweeter, or a few drops more lemon juice if it needs brightness.

Cool and store

Let the compote cool to warm or room temperature (it will thicken further as it cools). Transfer to a jar or airtight container and refrigerate for up to 7 days, or freeze up to 3 months. Reheat gently before serving if desired.

To serve

Spoon warm or chilled wild blueberry & cinnamon compote over yogurt, pancakes, waffles, oatmeal, toast, or vanilla ice cream. Garnish with chopped toasted nuts and a drizzle of honey or maple syrup if desired.