Preheat your oven to 380°F/195°C in natural convection/high and low static heat mode. Poke holes in the shortcrust pastry with a fork, then bake for 10-15 minutes.
Next, make the crème pâtissière: lightly boil the milk with the vanilla sugar. Once boiling, put on a low heat. Place the egg, sugar and flour in a bowl, mix well to prevent lumps, then add the mixture to the pan.
Mix gently with a whisk, gradually thickening the mixture to the consistency of crème pâtissière.
Wash the blackberries, then gently dry them in a clean tea towel.
Pour the crème pâtissière over the shortcrust pastry, arrange the blackberries on top and grate the zest of a lime with a zester for a pretty decoration. Enjoy!