Preheat oven to 400 °. Line cookie sheet with parchment paper.
In a large mixing bowl, whisk the sifted flour, granulated sugar, baking powder, and baking soda. Set aside.
Use a stick of frozen butter and grate along large holes on grater over the dry ingredients. Using either a pastry blender or your hands, mix butter and flour mixture just so it is evenly encorporated.
In a medium mixing bowl, whisk the heavy cream, sour cream, 2 mashed bananas and vanilla extract.
Using a bench blade, pour wet ingredients into the flour mixture until large clumps form. Rotate along side of the bowl until a ball forms. The dough will be sticky at this point, but as you work with it, the dough will come together.
Place dough on a lightly floured surface and pat into about a 8 in circle. Cut in half and form about a 4-5 in circle with both balls. Use a sharp, floured knife and cut the dough into small triangles; place on prepared baking sheets, about an 1 in apart. Put in fridge for 30 minutes to help firm up that butter.
Once pulled out of the fridge, brush each scone with heavy cream or milk. Put in the oven for 20-25 minutes. Scones will be light golden brown on top and around the edges. Set aside while you are making the bananas foster.
In a deep sided frying pan, melt your stick of salted butter on medium heat.
Add in your brown sugar to the butter and mix until small bubbles form.
Add in your heavy cream and mix together. Slice bananas diagonally and put in pan.
Pour in Rum. Put your lighter tipped towards the pan and flame should ignite the rum. It will take about 30 seconds for it to go out on its own; but you can shale the pan gently to hasten this if you need to.
Once flame is out, pour on top of scones and serve!
Scones are best eaten the day of, you can leave them room temperature in an airtight container for 2 days.