Combine the mashed banana, buttermilk, and vanilla into a medium bowl. Set aside.
½ cup (1 large, ripe banana) mashed banana, ¼ cup buttermilk, cold, ½ teaspoon vanilla extract
In the bowl of a stand mixer, combine the flour, brown sugar sugar, baking powder, baking soda, salt, cinnamon and nutmeg. Mix on low for minute.
2 ½ cups all purpose flour, ½ cup light brown sugar, packed, 1 ½ teaspoons baking powder, ¼ teaspoon baking soda, ½ teaspoon fine sea salt, ¾ teaspoon cinnamon, ⅛ teaspoon nutmeg
Add the cold, cubed butter to the flour mixture and mix on medium low speed, until the mixture looks sandy and the mixture resembles pea-sized crumbs.
½ cup (1 stick) unsalted butter, cut into cubes, cold
Only low speed, mix in the pecans.
⅓ cup pecans, coarsely chopped and toasted
Beat in the banana/buttermilk mixture, and mix until everything is just moistened. You may have some straggly bits that aren't completely mixed in. That's ok. Don't overwork the dough.
Scoop the dough onto the counter and, with floured hands, work dough into a 6 inch disc shape. The dough should be sticky. If it seems too dry, and won't stick together well, add another teaspoon of buttermilk.
With a sharp knife or bench scraper, cut the disc into 6 equal wedges.
Place the scones onto a baking sheet lined with parchment paper. Chill in the refrigerator for 30 - 45 minutes uncovered.
While the scones are chilling, preheat the oven to 400F.
Brush the tops of the scones with heavy cream. Sprinkle the tops with turbinado sugar.
1 tablespoon heavy cream or half and half, 1 tablespoon turbinado sugar, for sprinkling
Bake for 20-23 minutes or until golden brown. Remove the scones from the oven and let them cool for 10 minutes.
While the scones cool, whisk together the espresso, vanilla, and confectioner's sugar until combined. If the glaze is too thick add ½ teaspoon more of espresso until the glaze is the right drizzling consistency.
1 tablespoon prepared espresso or coffee, hot, ½ cup confectioner's sugar, ¼ teaspoon pure vanilla extract
Drizzle the scones with the glaze and sprinkle the remaining 1 tablespoon of pecans over the scones.
1 tablespoon pecans, finely chopped and toasted