Preheat oven to 400.
Combine dry ingredients.
Cut in butter with pastry blender.
Stir in bananas. Fold in buttermilk, egg, and vanilla. Batter will be sticky. Put wax paper on a plate. Put batter on wax paper. Cover with another sheet of wax paper.
Press dough into 3/4" thick circle. Put in freezer for 30 minutes.
Cut into 10 wedges. Place on parchment lined cookie sheet.
Brush with buttermilk and egg white. Sprinkle with sugar and/or cinnamon.
Bake 20 minutes until golden brown.
Cool on racks.
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