In a large bowl, whisk together flour, salt, and sugar.
Add cold, cubed butter and cut it into the flour until the mixture resembles coarse crumbs.
Add the egg and vanilla extract, and mix until the dough comes together into a smooth ball. Knead gently by hand if needed. You can use your kitchen machine with a dough hook attachment.
Flatten into a disk, wrap in plastic, and refrigerate for at least 30 minutes.
Roll out the chilled dough to about ¼-inch thickness and line a tart pan. Trim excess dough. Make sure to not stretch your crust too much or it will shrink.
Prick the tart base with a fork to prevent bubbles.
Line the crust with parchment paper and fill with pie weights (or dried beans).
Bake at 350°F (180°C) for 15 minutes.
Remove the parchment and weights, then bake 5 more minutes until lightly golden. Allow to cool completely. Each oven is different so look for golden brown.
In a saucepan, heat milk, matcha powder, and vanilla until just simmering. Remove from heat to infuse.
In a separate bowl, whisk together egg yolks, sugar, cornstarch, and salt until pale and smooth.
Temper the eggs by slowly whisking in the hot milk mixture.
Return the mixture to the saucepan and cook over medium heat, whisking constantly until thickened and bubbling (1–2 minutes).
Lower heat and cook 1–2 more minutes to fully cook the starch.
Remove from heat and stir in butter until smooth and glossy.
Strain through a fine sieve into a clean bowl, cover with plastic wrap pressed directly on the surface, and cool to room temperature. Refrigerate until set.
If desired, whip 200 g heavy cream until soft peaks form (chill bowl and whisk for best results).
Once the pastry cream is cooled, gently fold in the whipped cream to make a lighter, airy filling.
Spread the pastry cream (or pastry cream + whipped cream) evenly into the cooled, blind-baked tart shell.
Arrange fresh blueberries on top.
Dust lightly with powdered sugar before serving.
