Start by making the crème pâtissière filling by dissolving the cornstarch in 1 cup of cold milk in a suitable sauce pan over medium heat then add the granulated sugar and the remaining 2 cups of milk and mix well.

Next in a separate bowl add the vanilla and egg yolks and mix well, then slowly pour the egg yolks over the pot of milk while continuasly stirring until the crème pâtissière is thickened.

Now remove the crème pâtissière from the heat & mix in 1 tbsp of butter then cover & set aside in the refrigerator to cool down before using.

Meanwhile preheat the oven to 180°C or 350°F and bake the sliced puff pastry dough on a nonstick oven pan for 12-16 minutes or until puffed & golden brown, then pull out of the oven and set aside to cool down.

Finally fill the center of the puff pastry with the cool crème pâtissière filling then top with the strawberries & garnish with powered sugar then serve as desired.