Preheat your oven to 425°F. Line a baking sheet with parchment paper.

In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt. Add the cold, cubed butter and blend until the mixture resembles coarse crumbs.

Pour in the heavy cream and vanilla extract, stirring gently until just combined. Do not overmix.

Turn the dough out onto a floured surface and gently pat it into a 1-inch thick rectangle. Cut out rounds using a 2-inch biscuit cutter and place them on the prepared baking sheet.

Brush the tops of the biscuits with a little heavy cream. Bake for 12-15 minutes, or until golden brown. Remove from the oven and let cool.

In a medium bowl, combine the sliced strawberries and blueberries. Sprinkle with powdered sugar and lemon juice, tossing gently to coat. Let the fruit sit for about 10 minutes to release its juices.

To assemble, slice the shortcakes in half horizontally. Spoon a generous amount of the berry mixture onto the bottom half, followed by a dollop of whipped cream. Place the top half of the shortcake on top and add more whipped cream and berries if desired.