Preheat your oven to 400°F. Line a baking sheet with parchment paper.

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

Pour in the heavy cream and vanilla extract. Stir until just combined. Do not overmix.

Turn the dough out onto a floured surface and gently knead it a few times until it comes together. Pat the dough into a 1-inch thick rectangle.

Cut out shortcakes using a round biscuit cutter or a glass. Place them on the prepared baking sheet.

Brush the tops of the shortcakes with a little heavy cream for a golden finish. Bake for 15-18 minutes or until golden brown. Let them cool slightly on a wire rack.

While the shortcakes are baking, prepare the mixed berries. In a medium bowl, combine the berries, powdered sugar, and lemon juice. Toss gently and let sit for about 10 minutes to release their juices.

To assemble, slice the shortcakes in half horizontally. Spoon a generous amount of the mixed berries onto the bottom half, add a dollop of whipped cream if desired, and then place the top half back on.