Combine all of the ingredients in a blender and before you blend, slice the vanilla bean lengthwise and then run a knife down the inside of the bean to extract the seeds. Add these to the other ingredients in the blender and blend until smooth. Transfer ingredients into ice cream maker and voila. It's that easy. Literally I think going to the grocery store is the hardest part of the recipe. You may want to keep the ice cream in the freezer until just before you serve. This stuff melts fast!
If you don't have an ice cream maker, you can slice the bananas into thin pieces and freeze on parchment lined baking sheets, preferably overnight. Add these and the rest of the ingredients into a blender. Blend until smooth and serve immediately. This will have a bit more of a soft serve texture, but is still really delicious!