Preheat an oven to 400°F. Line a sheet pan with parchment paper, or spray with baking spray.
In a large mixing bowl, combine the flours, oats, sugar, baking powder, salt, and spices. Whisk to combine well.
Cut the butter into the flour mixture using a pastry cutter or your fingers. The fat should be in chunks no larger than a pea.
In a separate bowl, combine the syrup, cream and the sour cream. Stir well to combine.
Add the mashed bananas and the cream mixture to flour mixture and fold just until the flour is hydrated and the mix comes together. It should be slightly sticky, but if it's very sticky, fold in an additional 1/2 cup of all purpose flour.
Turn the dough out onto a floured surface and roll out into a rectangular shape (roughly 9”x13”). Cut the the rectangle into triangles of equal size using a very sharp knife. Transfer onto your sheet pan placing them about an inch apart.
Mix together the egg and the tbsp of water to create an egg wash. Brush each triangle lightly with the egg wash and sprinkle a generous pinch of turbinado sugar onto the tops of each triangle.
Bake the scones for 18-20 minutes or until golden brown.
While the scones are baking, make the maple glaze by combining the powdered sugar, melted butter, maple syrup and salt in a medium size mixing bowl. Whisk until smooth adding more maple syrup to thin the glaze to your preferred consistency.
Remove the scones from oven and transfer to a cooling rack. Allow to cool for 10 minutes before drizzling the glaze liberally over each scone.