Let the frozen acai packets sit at room temperature for 2–3 minutes so the plastic loosens slightly; slice or crack the packets into a few pieces while still mostly frozen.
Add the broken acai pieces to a high-speed blender or food processor first, then add the frozen banana chunks, frozen mixed berries, peanut butter and vanilla.
Start blending on low using short pulses to break up the frozen fruit. After it begins to combine, switch to a steady medium speed. If the mixture stalls, stop and press the fruit toward the blades with a tamper or the blender lid opening.
Add non-dairy milk 1 tablespoon at a time only if needed; you want a very thick, spoonable consistency rather than a pourable smoothie. Blend briefly between additions to avoid over-thinning.
When the base is smooth and holds its shape, scoop it into a bowl and smooth the top with the back of a spoon to create a flat surface for toppings.
Arrange granola, sliced banana, fresh berries and chia seeds over the bowl. Finish with a small drizzle of extra peanut butter if you like.
Serve immediately so the bowl stays thick and icy. If you prefer a firmer texture, pop the bowl in the freezer for 5–7 minutes before eating.