In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt, then set it aside.

Grate the butter to keep it from becoming too soft, which makes it easier to incorporate into the mixture.

Stir the grated butter into the flour mixture until it appears crumbly and dry.

Add cold heavy cream and milk to the mixture, and gently stir with a spatula or wooden spoon to combine, being careful not to overwork the dough to avoid dense shortcakes.

Flatten the dough to about 1 inch thick and cut out 6-7 biscuits using a lightly floured biscuit cutter, or shape the dough into a rectangle and cut it into squares.

Make your cuts as close together as possible; any scraps can be reformed to make additional biscuits, but they may become flatter and less uniform with each re-roll.

Brush the tops of the biscuits with heavy cream and generously sprinkle granulated sugar over them.

Bake the biscuits until they are light golden brown on both the tops and bottoms, then allow them to cool.

In a chilled bowl (preferably metal), combine cream, powdered sugar, and vanilla, then beat with an electric mixer on low speed until fluffy.