Roll out or unwrap your pie dough, and gently press it into your tart pan. Trim away any excess around the top. Prick the bottom of the dough, and fill with pie weights (if you don't have pie weights you can bake it without, just be prepared to press down any air pockets). Bake at 450F/230C for 10-12 minutes, or until the crust is golden brown (if using pie weights, remove the weights for the last 5 minutes of baking).
While the tart crust bakes, roll out or unwrap your second crust. Using star cookie cutters in various sizes, punch out star shaped pieces of crust. When the tart crust comes out, bake the stars at the same temperature for 6-7 minutes, or until golden brown. Immediately dust the stars with powdered sugar once you take them out.
To make the vanilla filling, combine the milk and granulated sugar in a small saucepan over medium-high heat. In a small bowl, whisk together the corn starch and egg yolks. Once the milk mixture is hot (but not boiling) pour half of it into the egg mixture, whisking constantly. Pour the egg mixture back into the saucepan, whisking the entire time, and bring to a boil. Boil for a few minutes until the mixture is thick. Remove the pan from the heat and whisk in the vanilla extract and butter.
Allow the mixture to cool to about room temperature before pouring it into the tart crust. Wrap the crust and filling with plastic wrap and chill in the refrigerator until the filling has set.
Layer the tart with slices of strawberries, whole blueberries, and the powdered sugar dusted stars.
Vanilla tart filling adapted from Betty Crocker's Cookbook (1978) pg. 302