01 - Preheat oven to 400°F. Line a baking sheet with parchment paper and set aside.
02 - In a mixing bowl, combine flour, sugar, baking powder, and salt. Add the cold cubed butter and cut in using a pastry blender or your fingers until the mixture resembles coarse crumbs.
03 - In a small bowl, whisk together the milk and egg. Pour the wet mixture into the dry ingredients and stir just until combined; do not overmix.
04 - Drop rounded spoonfuls of dough onto the prepared baking sheet, yielding about 6 to 8 shortcakes. Bake for 15 to 18 minutes until golden brown on top. Cool completely, then break into bite-sized pieces.
05 - While the shortcakes bake, combine the diced strawberries, granulated sugar, and lemon juice in a bowl. Let sit for 15 to 20 minutes to macerate and release their juices.
06 - In a chilled mixing bowl, whip the heavy cream with powdered sugar and vanilla extract using an electric mixer or whisk until soft peaks form.
07 - Layer shortcake pieces, macerated strawberries with their juices, and whipped cream in individual serving glasses or jars. Repeat for a second layer. Finish with a dollop of whipped cream and a few strawberry slices on top.
08 - Serve immediately, or cover and chill for up to 2 hours before serving to allow the flavors to meld.