In a blender, combine the frozen mixed berries, sliced banana, almond milk, and honey (if using). Blend until smooth.
In a separate bowl, stir together the chia seeds and 1/2 cup of water. Let the mixture sit for 5-10 minutes, stirring occasionally, until the chia seeds have absorbed the water and the mixture has thickened to a gel-like consistency.
Pour the berry smoothie into a jar, leaving some space at the top.
Spoon the chia seed mixture on top of the smoothie.
Add your favorite toppings, such as sliced fresh strawberries, blueberries, granola, and/or shredded coconut.
Seal the jar and refrigerate overnight.
In the morning, give the jar a good shake to mix everything together.