01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a mixing bowl, whisk together the flour, sugar, baking powder, and salt. Add the cubed cold butter and cut it in using your fingers or a pastry blender until the mixture resembles coarse crumbs.
03 - In a small bowl, whisk the heavy cream and egg together. Pour the wet mixture into the dry ingredients and stir gently just until the dough comes together.
04 - Turn the dough out onto a lightly floured surface and pat it into a ¾-inch thick round. Cut into small 1-inch squares or rounds suitable for individual trifle portions.
05 - Arrange the shortcake pieces on the prepared baking sheet and bake for 12 to 15 minutes until golden brown. Transfer to a wire rack and let cool completely.
06 - Toss the sliced strawberries with granulated sugar and lemon juice in a bowl. Let stand for 15 minutes until the berries release their natural juices.
07 - Using an electric mixer or whisk, beat the chilled heavy cream, powdered sugar, and vanilla extract on high speed until stiff peaks form.
08 - Layer shortcake pieces, macerated strawberries with their juices, and whipped cream in individual serving glasses. Repeat the layers once more, finishing with a generous dollop of whipped cream and a few fresh strawberry slices on top.
09 - Serve immediately, or refrigerate for up to 2 hours before serving to allow the flavors to meld.