In a medium bowl, combine the sliced strawberries, granulated sugar, and lemon juice. Gently toss them together and let them sit at room temperature for at least 15-20 minutes to macerate.

Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper. In a large bowl, whisk together the flour, sugar, baking powder, and salt.

Cut the cold butter into the dry ingredients using a pastry blender or your fingertips until the mixture resembles coarse crumbs. Gradually add the heavy cream, mixing until just combined and a soft dough forms.

Turn the dough out onto a lightly floured surface and gently pat it to a 1-inch thickness. Cut out 6-8 shortcakes using a 2.5-inch round cutter, re-rolling scraps as needed.

Place the shortcakes on the prepared baking sheet, brush the tops with a beaten egg, and sprinkle with a little extra sugar. Bake for 15-20 minutes, or until golden brown and cooked through. Let them cool on a wire rack.

In a cold bowl, using an electric mixer, beat the heavy cream, powdered sugar, and vanilla extract on high speed until stiff peaks form.

Once the shortcakes are cool, slice each one horizontally. Place the bottom half on a serving plate, add a generous spoonful of macerated strawberries, and top with a dollop of whipped cream.

Cover with the top half of the shortcake and serve immediately, garnished with additional strawberries and a sprinkle of powdered sugar if desired.