1/2 cup quick oats, dry (unprepared)
1 small or medium extra ripe banana, frozen
3/4 cup vanilla soy milk (or choc for a choc/banana smoothie)
Put the oatmeal in a blender and blend it until it's as fine as flour. Then, add the peeled frozen banana (make sure it's banana-bread-ripe so the smoothie/ice cream is sweet and not bitter).
Finally, pour in the soy milk (how much of the 3/4 cups depends on the consistency you like your smoothies). Blend until the banana gets mashed and this mixture is just incorporated.
Taste. If its too sweet or too thick, add some ice and a bit of soy milk to help stir it up.
If its too thin, add some ice to thicken it.