In a large mixing bowl, whisk together both flours, baking powder, cinnamon, and salt. Set aside.
1 ½ cups all-purpose flour, 1 cup cake flour, 2 ½ teaspoons baking powder, 2 teaspoons ground cinnamon, 1 teaspoon kosher salt
Grate the frozen butter using a box grater.
5 tablespoons unsalted butter
Add the grated butter to the flour mixture and combine with a pastry cutter, two forks, or your fingers until the mixture comes together in pea-sized crumbs.
Place in the freezer as you mix the wet ingredients together.
Whisk together in a small bowl the mashed banana, sour cream (or Greek yogurt), brown sugar, egg, and maple syrup.
1 cup very ripe banana, ¼ cup full-fat sour cream , ½ cup dark brown sugar, 1 large egg, 2 teaspoons pure maple syrup
Drizzle over the flour mixture, then mix together until everything appears moistened
Dump dough onto a lightly floured counter top. Dip your hands in flour and work the dough into an 8-inch disc as best you can (does not have to be perfect). Dough may be sticky. If it’s too sticky, add a little more flour. Once in an 8-inch disc, cut into 8 evenly-sized wedges using a sharp knife or bench scraper.
Place scones on a parchment-lined baking sheet, 2-3 inches apart and refrigerate for at least 15 minutes.
Preheat oven to 400ºF.
While dough is chilling, prepare crumb topping. In a large mixing bowl, mix all ingredients with your hands, squeezing together to form large crumbs or clumps. Set aside
4 tablespoons unsalted butter, ½ cup dark brown sugar, 1 tablespoon granulated sugar, 2 tablespoons all-purpose flour, pinch of kosher salt
Remove scones from the refrigerator and brush tops with heavy cream then sprinkle with crumb topping. Bake for 22-25 minutes or until golden brown. Allow to cool on trays
heavy cream for brushing tops