In a large bowl, whisk together the flour, sugar, baking powder and salt. Work the butter into the flour mixture with your fingertips or with a pastry blender until pea size pieces form.
In a small bowl, whisk together the heavy cream, sour cream and vanilla. Stir the cream mixture into the flour mixture until a shaggy dough is formed.
Turn the dough out onto a lightly floured surface. Fold the dough over onto itself a couple of times. Don’t overwork the dough. Pat the dough into a 6 1/2-inch diameter, 3/4-inch thick round. Cut the dough into 8 wedges.
Place the scones 2 inches apart onto the prepared baking sheet. Chill the scones in the refrigerator for 15-20 minutes.
Preheat the oven to 375ºF (190ºC). Brush the tops of the scones with egg wash. Bake until the scones are golden brown, about 16-20 minutes. Transfer the scones to a cooling rack. Brush the tops of the cooled scones with vanilla bean icing.
Vanilla Bean Icing
In a medium bowl, whisk together the powdered sugar, butter, vanilla, 1 tablespoon of milk and the salt. Add additional milk as needed to reach your desired consistency.