To serve, whip three pints of heavy cream with about one and one-half cups confectioners' sugar, and set out with about five pints of fresh berries for guests to assemble their shortcakes.
Preheat oven to 400 degrees. Whisk together flour, granulated sugar, baking powder, and salt in a medium bowl. Using a pastry blender, cut in the butter until thoroughly combined. Using a rubber spatula, stir in the cream.
Turn out dough onto a lightly floured work surface. Pat dough into a rectangle about 1/2 inch thick. If dough is too soft to cut smoothly, place in freezer until firm enough. Using a 2 1/4-inch fluted cutter, cut out rounds, and transfer them to a parchment-lined baking sheet. Brush tops with egg; sprinkle with sanding sugar. Bake until edges of shortcakes begin to turn golden brown, about 20 minutes.