2½ cups pastry flour
2½ teaspoons granulated sugar
2 tablespoons plus 1 teaspoon fresh baking powder (baking powder looses its rising ability in a few months – if yours is more than 3 or 4 months old, buy a new container for extra fluffy biscuits)
4½ teaspoons kosher salt
1½ cups (3 sticks) plus 1 tablespoon unsalted butter, chilled and cubed
6 cups all-purpose flour, plus more for rolling out your dough
3¼ cups buttermilk, chilled
1 large egg, lightly beaten
2 tablespoons heavy cream