01 - Preheat oven to 400°F. Line a baking sheet with parchment paper and set aside.
02 - In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, and salt. Add the cold cubed butter and cut it in using a pastry blender or your fingertips until the mixture resembles coarse crumbs with pea-sized pieces of butter throughout.
03 - In a small bowl, whisk together the whole milk and egg until combined. Pour the wet mixture into the dry ingredients and stir gently just until the dough comes together — avoid overmixing.
04 - Drop rounded spoonfuls of dough onto the prepared baking sheet, yielding about 6 to 8 shortcakes. Bake for 15 to 18 minutes, or until the tops are golden brown and a toothpick inserted in the center comes out clean. Transfer to a wire rack and cool completely, then break into bite-sized pieces.
05 - While the shortcakes bake, combine the diced strawberries, granulated sugar, and lemon juice in a medium bowl. Toss gently and let sit at room temperature for 15 to 20 minutes until the berries release their juices.
06 - In a chilled mixing bowl, beat the heavy whipping cream with an electric mixer on medium speed. Gradually add the powdered sugar and vanilla extract, continuing to whip until soft peaks form — the cream should hold its shape when the beaters are lifted.
07 - In individual serving glasses or jars, create layers starting with shortcake pieces at the bottom, followed by a generous spoonful of macerated strawberries and their juices, then a dollop of whipped cream. Repeat for a second layer. Finish each trifle with a final swirl of whipped cream and a few strawberry slices on top.
08 - Serve the trifles immediately, or cover and refrigerate for up to 2 hours before serving to allow the flavors to meld.