Preheat your oven to 350°F (180°C).

To make the choux dough: Melt the butter in the boiling liquid (water, milk, sugar, and salt). Add the flour off the heat, stirring vigorously.

Dry the dough: Return the pan to low heat and stir with a spatula for 4 to 5 minutes until the dough pulls away from the sides of the pan.

Add the eggs: Off the heat, let the dough cool slightly, then mix in the eggs one at a time until the dough is smooth and of medium consistency.

Pipe the dough into small mounds and bake for 25 to 30 minutes at 350°F (180°C).

To make the caramelized apple pastry cream:

Caramelize the apples in a skillet with sugar and butter.

In a saucepan, heat the milk, half the sugar, and vanilla over medium heat until it comes to a boil.

In a bowl, mix the caramelized apples with the eggs, add the remaining sugar, and whisk until pale. Add the cornstarch and mix well.

Gradually add the hot milk mixture, whisking constantly, until smooth (off the heat).

Return the mixture to the heat and cook, stirring, until the cream thickens.

Remove from the heat, stir in the butter, cover with plastic wrap directly on the surface, and let cool.

Fill the cream puffs and enjoy!