In a large mixing bowl, cream together the butter and sugar until light and fluffy, about 3-5 minutes. Gradually add the flour and beaten egg, mixing until a smooth dough forms. Shape into a disc, wrap in plastic wrap, and chill in the refrigerator for at least 30 minutes.

Preheat your oven to 350°F (175°C). Roll out the chilled dough to about ¼ inch thick, transfer to a 9-inch tart pan, pressing into the sides and trimming excess. Line with parchment paper and fill with pie weights. Blind bake for 20-25 minutes until golden. Let cool and remove weights.

In a medium saucepan, whisk together the egg yolks and sugar until slightly thickened. Gradually stir in warmed milk infused with vanilla bean seeds. Cook over medium heat, whisking continuously, for about 8-10 minutes until thickened. Transfer to a bowl, cover with plastic wrap touching the surface, and chill for at least 2 hours.

Once the cream is chilled, spoon it into the cooled crust, spreading it evenly. Ensure the filling reaches the edges for a polished look. Refrigerate for another 30 minutes to set.

Decorate the tart with fresh berries, dusting with powdered sugar. Optionally, add toasted almond slivers and mint leaves. Serve chilled.