preheat oven to 325
In a medium bowl mash banana with vanilla
Add sugar, eggs, 3 T sour cream, milk, and buttermilk
In a separate larger bowl combine all dry ingredients
Add the wet ingredients to the dry and mix well. ( because there isn't any gluten to worry about you don't need to be paranoid about over mixing)
Fill cups only 2/3 full and bake for 20 minutes or until just done. Transfer to a plate or wire rack as soon as possible as gluten free cupcakes can get soggy quickly.
In a small sauce pan over medium heat stir milk and flours together until they form a paste. Cool in the fridge or over an ice filled bowl
Cream together butter, sugar and vanilla until fluffy
Combine the paste and butter mix and mix until it forms a creamy light frosting.