For Preparation:
Preheat oven to 425°F (220°C).

For the Filling:
In a medium saucepan, heat the milk and vanilla bean to a boil over medium heat.
Turn off the heat and let it infuse for 15 minutes.
In a bowl, whisk egg yolks and sugar until light and fluffy.
Add cornstarch and whisk until no lumps remain.
Whisk in 1/4 cup of the hot milk mixture until incorporated.
Whisk in the remaining hot milk mixture.

Pour the mixture through a strainer back into the saucepan.
Cook over medium-high heat, whisking constantly, until thickened.
Remove from heat and stir in butter.
Let cool slightly, then cover and chill for at least 2 hours.

For the Pastry:
In a large saucepan, bring water, butter, salt, and sugar to a boil.
Remove from heat and add all-purpose flour, stirring until incorporated.
Return to heat and cook, stirring, for 30 seconds.
Transfer mixture to a mixer and mix at medium speed.

Add eggs one at a time, mixing well after each addition.
Pipe dough onto a lined baking sheet.
Brush with egg wash.
Bake at 425°F (220°C) for 15 minutes, then reduce heat to 375°F (190°C) and bake for 25 more minutes.

For the Glaze:
Heat cream in a saucepan until boiling, then pour over chopped chocolate.
Whisk until melted and smooth.
Dip the tops of eclairs in the warm chocolate glaze and chill for at least 1 hour.
Serve chilled and enjoy your delicious eclairs!