In a medium bowl or 1-quart measuring cup, combine the milk and chia seeds and whisk. Stir occasionally for 10 minutes to avoid clumping. Allow the mixture to soak overnight in the refrigerator.
The next day, transfer the chia pudding to a high-speed blender. Add any desired ingredients (see our list of recommendations below!). Process on medium speed to start, using a tamper as you need to get everything going. Gradually increase the speed of the blender to high until smooth.
Add desired toppings and enjoy!