Get out and measure all of your ingredients.
In a small saucepan, combine blueberries, lemon juice, granulated sugar, and 2 tablespoons water.
Combine cornstarch and water. Stir until dissolved and add to berry mixture, if desired.
Cook over medium heat, stirring frequently, until blueberries begin to break down and juices boil and thicken, about 5 minutes.
Remove from heat, and transfer to a small bowl. Place bowl in a larger bowl of ice water, and stir mixture occasionally until cold.
In a separate bowl, combine cream, confectioners' sugar, and vanilla.
Beat until stiff peaks form.
Fold in ⅓ cup of the blueberry sauce.
Carefully stir until blended.
Divide among 4 dessert dishes, and spoon remaining sauce over tops.
Serve immediately and enjoy!