01 - Combine flour, salt, and powdered sugar in a large bowl. Add cold butter and cut it into the flour with fingertips until the mixture resembles coarse crumbs. Incorporate the egg and mix just until a smooth dough forms. Shape into a disk, wrap in plastic, and refrigerate for 30 minutes.
02 - Preheat oven to 350°F. Roll out dough and fit into a 10-inch tart pan. Prick the base with a fork, line with parchment, and fill with pie weights. Bake for 20 minutes, remove weights and parchment, then bake another 10 minutes until lightly golden. Cool completely.
03 - Heat milk with vanilla over medium heat until just simmering. In a separate bowl, whisk together egg yolks and sugar until pale, then whisk in cornstarch. Gradually whisk in a little hot milk, then add the mixture back to the pot. Cook, stirring constantly, over medium heat until thickened. Remove from heat, whisk in butter, and cover with plastic wrap touching the surface. Chill until cold.
04 - Wash, hull, and slice strawberries according to preference.
05 - Spread pastry cream evenly over cooled tart shell. Arrange strawberries decoratively on top.
06 - Heat apricot jam with water until melted, then brush over strawberries with a pastry brush to give a glossy finish.
07 - Refrigerate assembled tart for at least 1 hour before slicing and serving.