In a large bowl, combine flour, baking powder, cinnamon, and salt. Stir to combine.
Add in grated butter and cut in with a fork or pastry cutter until crumbly. Set in the freezer to keep cold.
In a separate bowl mash bananas and add in sour cream, 2 tbsp heavy cream, egg, brown sugar, and vanilla. Whisk to combine.
Pull the flour/butter mixture from the fridge and in the wet ingredients, folding until just combined. Add the walnuts and chocolate chips and mix until just combined.
Dump the dough onto a lightly floured surface. The batter will be sticky so be sure to also dust the top of the dough and your hands. Softly fold the dough three to four times. Again, do not over mix. Form into a disc. Wrap in plastic wrap and place in the freezer for about 15 minutes.
Preheat your oven to 375 degrees.
Pull the scone disc from the freezer, unwrap, and cut into 8 triangles. Place the triangles on a lined baking sheet and use the remaining 1 tbsp of heavy cream to coat the top and sides.
Bake for 20 minutes until a dark golden brown.
Notes
Storage: Store at room temperature 1-2 days in a sealed container or in the fridge up to 3 days.
Freeze: You can freeze unbaked scone dough up to 3 months and bake from frozen, adding an additional 2-3 minutes. Freeze baked scones up to 1 month.