Gruyere, Apple and Sage Scones

From Good Life Eats  Ingredients: 4 cups flour 4 teaspoons baking powder 3/4 teaspoon salt 2 teaspoons sugar 1 cup very cold butter 2 large eggs, plus an extra for egg wash 4 – 5 tablespoons buttermilk, plus extra for egg wash 2 green or red apples, finely diced...