Prepare the Strawberries:

1. In a large bowl, combine sliced strawberries, sugar, lemon juice, and vanilla extract. Toss gently to coat.
2. Let strawberries macerate at room temperature for 30 minutes to 2 hours, stirring occasionally, until they release their juices and create a syrup.

Make the Shortcakes:

3. Preheat oven to 425°F (220°C). Line a baking sheet with parchment paper.
4. In a large bowl, whisk together flour, sugar, baking powder, and salt.
5. Add cold butter cubes and use a pastry cutter or your fingers to work the butter into the flour until the mixture resembles coarse crumbs with pea-sized pieces of butter remaining.
6. In a small bowl, whisk together heavy cream, egg, and vanilla extract.
7. Pour the wet ingredients into the dry ingredients and stir with a fork until just combined. Do not overmix; the dough should be slightly shaggy.
8. Turn dough out onto a lightly floured surface and gently pat into a 1-inch thick rectangle.
9. Use a 3-inch round biscuit cutter to cut out 6-8 shortcakes, pressing straight down without twisting. Gather scraps, pat out gently, and cut remaining biscuits.
10. Place shortcakes on prepared baking sheet, spacing them 2 inches apart. Brush tops with heavy cream and sprinkle with coarse sugar.
11. Bake for 12-15 minutes, until golden brown on top and cooked through. Transfer to a wire rack to cool slightly.

Make the Whipped Cream:

12. In a large bowl or stand mixer, beat cold heavy cream, powdered sugar, and vanilla extract on medium-high speed until soft peaks form, about 2-3 minutes. Do not overbeat.

Assemble:

13. Split each warm or room-temperature shortcake in half horizontally.
14. Place bottom half on a plate, spoon generous amount of macerated strawberries and their juices over it, add a dollop of whipped cream.
15. Top with the other half of the shortcake, more strawberries, and another dollop of whipped cream.
16. Serve immediately while shortcakes are fresh.