Add the flour, sugar, salt and baking powder to the bowl of a food processor and pulse a few times. Add the butter and continue to pulse until the mixture is crumbly. Add the milk and continue to pulse until moistened. Turn out onto a clean, lightly floured work surface and shape into a circle. Cover with plastic wrap and chill for 30 minutes.
Roll the dough out into a circle 1-inch thick. Use a 3-inch biscuit cutter to cut biscuits. Place on a greased baking sheet. Beat the egg with 1 tablespoon water. Brush the tops of the biscuits with the egg wash then sprinkle with the turbino sugar.
Bake until golden brown, about 18 to 20 minutes. Let cool on a cooling rack.
For the macerated balsamic strawberries:
In a medium mixing bowl stir together the strawberries, sugar and balsamic vinegar. Let stand at room temperature until the juices from the strawberries are released and a syrup forms, about 30 minutes.
For serving:
Add the chilled heavy cream and sugar to the bowl of a stand mixer. Beat on high until stiff peaks form, about 1 minute.
Split the biscuits in half and spoon some of the strawberry mixture in between. Top with a scoop of whipped cream and the other half of the biscuit. Garnish with basil.
Notes
Let the strawberries macerate for at least 30 minutes before serving. This draws out their juices and creates a naturally sweet syrup that soaks beautifully into the shortcake.