Sift the flour over a large bowl.
Cut the butter into small pieces and, using your fingertips, work it together with the flour until it is a sandy texture. Try to keep the butter as cold as possible.
Dig a well in the center of the flour mixture.
Crack the egg into the well.
Add the sugar and mix all the ingredients with your fingertips, being careful not to overmix.
Flatten the dough with your hands until it comes together.
Roll the dough into a ball, then quickly flatten the dough between two sheets of cling film.
Refrigerate the flattened dough for 30 minutes.
Preheat the oven to 350 degrees F. Grease a 9- or 11-inch tart pan with a removable bottom.
Using a rolling pin, flatten the dough between the sheets of cling film into a large disc.
Remove the cling film and transfer the dough into the tart pan.
Line the bottom of the crust with a piece of parchment paper and spread ceramic pie weights, rice, or beans on top.
Bake the crust until lightly golden, about 15 minutes.
Allow the crust to cool for a few minutes, then transfer it to a cooling rack to cool completely.
Pour the milk into a saucepan together with the vanilla pod and seeds.
Stir and heat the mixture over medium-low heat until it starts bubbling slightly.
Whisk the yolks and sugar in a bowl until the mixture is pale and fluffy.
Whisk in the flour and cornflour.
Very gradually pour the hot milk over the yolk mixture, whisking constantly.
Pour the custard mixture back into the saucepan and cook for about 3 minutes, stirring constantly.
Turn off the heat.
Stir in the butter and Grand Marnier and stir it well.
Remove the vanilla pod.
Transfer the pastry curd into a cold bowl.
Cover it with cling film, creating contact with the cream so a skin doesn’t form.
Spread the pastry cream over the crust.
Arrange the strawberries cut in halves or slices over the cream.
Slice and serve!