In a high-speed blender, combine the almond milk, frozen banana, peanut butter, flax seeds, and vanilla. Blend until very smooth, stopping to scrape down the blender as needed.
At this point you can make adjustments, adding an extra tablespoon of water or milk if the smoothie isn't blending well, or you can add a handful of ice cubes to help it thicken up into more of a slushy texture. Just keep in mind that additions will dilute the flavor slightly, so keep them to a minimum. You can also add a squeeze of honey, or a splash of maple syrup, for extra sweetness.
Once the smoothie is blended, it's ready to serve right away for the best taste and texture. Top with extra sliced banana or a drizzle of peanut butter, if you'd like.
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Notes
Nutrition information is for the entire recipe. This information is automatically calculated, and is just an estimate, not a guarantee.See the full post above for substitution notes & tips. Leftover smoothie can be frozen in a mini ice pop mold (affiliate link), if you'd like a sweet treat later.