Preheat your oven to 375°F (190°C). Line two large rimmed baking sheets with unbleached parchment paper and set aside.

In a medium-sized, heavy-bottomed saucepan over medium heat, combine the butter, milk, and salt. Heat until the butter melts and the mixture begins to simmer.

Remove the pan from the heat, add the pastry flour, and stir vigorously until thoroughly combined.

Return to low heat, stirring constantly until the mixture forms a ball and leaves a film on the bottom of the pan (about 2 minutes).

Remove from heat and let the dough cool for at least 3 minutes until it's no longer hot to the touch.

Transfer the cooled dough to a blender or food processor, pour 5 eggs on top, and process until smooth (about 2 minutes).

Check the consistency: the dough should be shiny and soft, falling off the spoon without being runny. If it’s not shiny enough, pulse again. If it’s too stiff, add more beaten egg bit by bit until it’s perfect for piping.

Pipe your choux into little puffs and fill them with your desired filling.