01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until evenly combined.
03 - Add the cubed cold unsalted butter to the dry mixture. Using a pastry blender or your fingertips, cut the butter in until the mixture resembles coarse crumbs with pea-sized pieces remaining.
04 - In a separate small bowl, whisk together the heavy cream and egg. Pour the wet mixture into the dry ingredients and stir gently just until a soft dough comes together. Do not overmix.
05 - Turn the dough out onto a lightly floured surface. Gently pat it into a ¾-inch thick round. Using a knife or biscuit cutter, cut into small squares or rounds approximately 1 inch in size for individual trifle portions.
06 - Arrange the shortcake pieces on the prepared baking sheet. Bake for 12 to 15 minutes until the tops are golden brown. Transfer to a wire rack and let cool completely.
07 - Place the hulled and sliced strawberries in a bowl. Add the granulated sugar and lemon juice, tossing gently to coat. Let the mixture stand at room temperature for 15 minutes until the berries release their natural juices.
08 - In a chilled mixing bowl, combine the cold heavy cream, powdered sugar, and pure vanilla extract. Beat on high speed using an electric mixer until stiff peaks form, being careful not to over-whip.
09 - In individual serving glasses, begin layering: place a few shortcake pieces at the bottom, spoon macerated strawberries with their juices over the cake, and add a generous dollop of whipped cream. Repeat the layers once more. Finish each trifle with a final dollop of whipped cream and a few fresh strawberry slices on top.
10 - Serve the trifles immediately, or cover and refrigerate for up to 2 hours before serving to allow the flavors to meld.