01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large 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 - Whisk the heavy cream and egg together in a small bowl. Pour into the dry mixture 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 layering in trifle glasses.
05 - Arrange the shortcake pieces on the prepared baking sheet. Bake for 12 to 15 minutes until golden brown on top. Transfer to a wire rack and cool completely.
06 - Toss the sliced strawberries with granulated sugar and lemon juice in a medium bowl. Let stand for 15 minutes until the berries release their natural juices.
07 - In a chilled bowl, beat the heavy cream, powdered sugar, and vanilla extract on high speed using an electric mixer 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. Finish each trifle with a dollop of whipped cream and a few fresh strawberry slices on top.
09 - Serve immediately, or cover and refrigerate for up to 2 hours before serving.