1Preheat oven to 400F. In a bowl, stir together the flour, sugar, baking powder, baking soda and salt. Add the butter and blend it with a fork, whisk, pastry blender or your fingers (or do it all in the food processor, if you have one), leaving some lumps no bigger than a pea.
2In a small bowl, stir the buttermilk, egg and vanilla together with a fork. Add to the flour mixture and stir just until combined. Pat the dough out about an inch thick on a parchment-lined sheet and cut into rounds or wedges; brush with milk or cream and/or sprinkle with sugar. Pull them apart, leaving at least an inch between them, and bake for about 20 minutes, or until golden.
3To make the glaze, whisk together the icing sugar, milk and vanilla; drizzle it over the scones while they're still warm.