1In a one cup measuring cup, place 1 tbsp vinegar and fill the rest of the cup with milk. Set aside and let sit for 5 minutes. (this is your buttermilk).
2Place banana, almonds, oatmeal, flax and berries in blender and pulse a few times. Add yogurt, juice and "buttermilk" and blend to combine. Add ice cubes 2 at a time and pulse to break up, then blend to desired consistency.
If you prefer, you can use 1 cup buttermilk if you have it on hand. Then omit milk and vinegar.