Begin by creaming together the softened butter and sugar until fluffy, about 3 minutes. Incorporate the beaten egg and gradually add flour until a dough forms. Shape into a disk, wrap in plastic, and chill for 30 minutes.

Preheat the oven to 375°F (190°C). Roll out the chilled dough to about ¼-inch thickness. Fit into a 9-inch tart pan, trimming excess. Prick the bottom with a fork, cover with parchment paper, and fill with pie weights. Chill in the freezer for 15 minutes.

Bake the tart crust for 15-20 minutes or until golden. Remove weights and parchment, and let cool on a wire rack.

For the pastry cream, combine whole milk and vanilla bean seeds in a saucepan, bringing to a simmer. In another bowl, whisk egg yolks and sugar until pale. Gradually add warm milk, whisking continuously. Return to heat and cook, stirring, until thickened, about 5-7 minutes.

Strain the pastry cream into a bowl, cover with plastic wrap directly on the surface, and chill in the refrigerator for at least 1 hour.

Pour the chilled pastry cream into the cooled tart shell and smooth the surface. Chill the tart for at least 30 minutes.

Dust with powdered sugar before serving and garnish with fresh berries. Slice and enjoy!