Banana Bread Scones From Samantha Seneviratne

Name: Banana Bread Scones From Samantha Seneviratne
Ingredients: 1 extra-large, extra-ripe banana, mashed (1/2 cup); 1/3 cup heavy cream, plus more for brushing; 1 large egg, lightly beaten; 1 teaspoon pure vanilla extract; 2 cups all-purpose flour; 1/3 cup packed dark brown sugar; 2 1/2 teaspoons baking powder; 1/2 teaspoon kosher salt; 1/2 cup (1 stick) cold unsalted butter, cut into roughly 1/2-inch pieces; 2 1/4 ounces semisweet chocolate, chopped (1/2 cup); 1 1/4 ounces hazelnuts, toasted, skinned, and finely chopped (about 1/4 cup); Sanding sugar for sprinkling (or turbinado or granulated)