01 -
Heat the milk with half the sugar until steaming. In a bowl, whisk egg yolks, remaining sugar, cornstarch, and salt until smooth. Slowly whisk in half the hot milk, then return everything to the pan and cook over medium heat until thick and bubbling. Strain, whisk in vanilla and butter, cover the surface with plastic wrap, and chill for at least 2 hours.
02 -
Preheat the oven to 425°F (220°C). Line two baking sheets with parchment. In a medium saucepan, bring water, milk, butter, sugar, and salt to a full boil.
03 -
Add the flour all at once and stir firmly with a wooden spoon until a smooth dough forms. Keep stirring over medium heat for 1-2 minutes, until the dough pulls away from the pan and leaves a thin film on the bottom.
04 -
Transfer the dough to a bowl and cool for 5 minutes. Beat in the eggs one at a time, mixing fully after each addition, until the dough is glossy and falls from the spoon in a thick V shape.
05 -
Spoon the dough into a piping bag fitted with a large round or French star tip. Pipe 12 lines, each about 4 inches long, onto the prepared sheets. Bake for 10 minutes, reduce heat to 350°F (175°C), and bake 20-25 minutes more until deep golden and firm.
06 -
Turn off the oven, crack the door, and let the shells sit for 5 minutes. Move them to a rack and cool completely before filling.
07 -
Place chopped chocolate in a heatproof bowl. Heat the cream until steaming, pour it over the chocolate, and let stand for 1 minute. Stir until smooth, then stir in the butter.
08 -
Whisk the chilled pastry cream until smooth and transfer it to a piping bag with a small tip. Poke two holes in the bottom of each shell and pipe in the cream. Dip the tops in warm ganache and let set for about 10 minutes before serving.