Makes roughly 4 cups.
Wash the blueberries in cold water and be sure all stems are removed.
Place a large pot over medium high heat. Add Merlot, sugar and vanilla.
Bring to a simmer then add in the blueberries. Cook until the berries just begin to burst (roughly 15 minutes).
Mix cornstarch with cold water and whisk into the simmering berries. Continue to cook for an additional 5 minutes.