In a bowl or jar, whisk together the milk, vanilla extract, and sweetener.
Stir in the chia seeds, mixing thoroughly to prevent clumping.
Fold in the blueberries, or blend some into a puree for a smoother, more intense flavor.
Cover and refrigerate for at least 4 hours, preferably overnight, stirring occasionally during the first hour to prevent clumping.
Top with optional toppings before serving.