Preheat oven to 220 C/ 200 C fan/ 425 F and line a baking tray with baking paper.
Rub the flour, baking powder, salt, vanilla sugar and butter together in a medium sized bowl until it resembles fine bread crumbs.
Add the yogurt and milk and stir with a wooden spoon until it forms a soft dough. Turn out onto a floured board and knead for a minute or so until smooth.
Flatten the dough your hands and, with a rolling pin, roll out into a rectangle about one inch thick. Cut into eight even sized pieces and place on the baking paper.
Glaze with the beaten egg and sprinkle with caster sugar.
Bake for 12-15 minutes in the middle of the oven until well risen and golden. Transfer to a wire rack to cool completely.
To prepare the strawberries: slice large ones and quarter the small ones. Place them in to a bowl. Pour over the balsamic vinegar and sprinkle over the caster sugar and the freshly ground black pepper. Leave at room temperature for half an hour.
To prepare the cream: whip the cream with a whisk until it begins to thicken. Sprinkle over the vanilla sugar and whip until the cream forms soft peaks. Refrigerate until needed.
To serve, slice each shortcake into half, spoon over some whipped cream and top with the sliced strawberries in syrup. Serve immediately.