Blend the berry mixture: Add the milk, mixed berries, maple syrup, vanilla extract, and pinch of salt to a blender. Blend until completely smooth and evenly combined.
Add the chia seeds: Pour the blended mixture into a bowl, jar, or other container. Add the chia seeds and stir thoroughly, making sure the seeds are distributed throughout the liquid.
Stir it a second time: Let the mixture rest for about 5 minutes. Give it another thorough stir, breaking apart any clusters of chia seed that may have formed. This simple second stir is one of the easiest ways to prevent clumpy pudding.
Chill until thick: Cover the container and refrigerate the pudding for at least 2 hours. For an easy berry chia pudding overnight breakfast, simply leave it in the refrigerator until morning.
Adjust and serve: Stir the chilled pudding before serving. If it has become thicker than you prefer, mix in a small splash of milk until it reaches your desired consistency. Spoon it into bowls or jars and finish with your favorite toppings.