Preheat oven to 425°F.

Add flour, sugar, salt, and butter to a bowl, cut butter into dry ingredients until it resembles a coarse meal.

Add just enough water to combine dough.

Wrap dough in plastic and chill for 30 minutes.

Roll out dough into a 10 – 11 inch circle on a lightly floured surface.

Place in tart pan, press into place, trim edges, and poke with a fork to release steam.

Bake for about 20 minutes, until lightly brown.

Heat the cream until just about to boil.

Pour over the chocolate stirring until chocolate melts.

Spread over the bottom of the baked pastry.

Chill.

Add milk to a small saucepan, reserving a couple of tablespoons.

Add the sugar and salt to the milk.

Split the vanilla bean pod, scrape out the seeds, adding them to the milk.

In a small bowl, whisk the corn starch and flour.

Whisk the egg yolks and remaining milk into the corn starch and flour.

Heat the milk to a simmer, stirring to dissolve sugar.

Whisk a small amount of the hot milk into the egg yolks.

Pour the egg/milk mixture into the hot milk, stirring constantly, bring to a boil.

Continue stirring until mixture thickens, remove from heat.

Strain through a sieve to remove any egg lumps.

Stir in butter and vanilla extract if using.

Top with plastic wrap, pressing it on top of the hot mixture.

Cool and spread into the ganache filled crust.

Top with blueberries and chill before serving.