First, you'll want to prepare your fruit. If you are using fresh berries, give them a good rinse under cold water. I like to soak them for a few minutes in a large bowl of water with a tablespoon of vinegar to ensure they are thoroughly clean before draining them.
Next, combine all your ingredients in a high-speed blender. Add the mixed berries, banana, almond milk, and chia seeds. Secure the lid and blend on high until the mixture is completely smooth and has a creamy, consistent texture. If you prefer a thinner smoothie, feel free to add a little more almond milk.
Once blended, pour the smoothie into two glasses. You can enjoy it as is, or add some toppings for extra flair. A few whole berries or a sprinkle of crushed nuts on top adds a nice touch. This smoothie is best served immediately while it's fresh and cold.