Preheat the oven to 180°C / 355°F and line 2 baking sheets with baking paper.

Combine 40 g of softened unsalted butter, 2 g salt, 50 g granulated sugar, and 50 g all-purpose flour in a mixing bowl until homogeneous.

Roll the craquelin dough between 2 sheets of baking paper to a 3 mm thickness.

Cut discs slightly smaller than the intended cream puffs and freeze them until needed.

Bring 150 g water, 65 g unsalted butter, 2 g salt, and 2 g granulated sugar to a boil in a saucepan.

Remove the saucepan from the heat and add 85 g all-purpose flour all at once.

Stir the mixture until a smooth dough forms, then cook it over medium heat for 1 to 2 minutes while stirring vigorously.

Transfer the choux dough to a mixing bowl and whisk briefly to cool it slightly.

Add 160 g whole eggs in 3 additions, whisking thoroughly after each addition until the dough is smooth, glossy, and falls from the whisk in a ribbon.

Pipe the choux dough into 8 evenly sized mounds on the lined baking sheets.

Place one frozen craquelin disc on each choux mound and bake for about 30 minutes until puffed and deeply golden.

Heat 450 ml whole milk with 60 g crushed coffee beans in a saucepan until boiling.

Remove the coffee milk from the heat and infuse it for 30 minutes.

Whisk 5 egg yolks with 100 g granulated sugar until smooth, then whisk in 70 g all-purpose flour.

Strain the infused coffee milk to remove the crushed coffee beans and combine it with 250 ml heavy cream.

Whisk the coffee milk mixture into the egg-yolk mixture until fully combined.

Return the pastry cream mixture to the saucepan and cook over medium heat, whisking continuously until thickened.

Transfer the hot coffee pastry cream directly to a piping bag and chill until completely cold.

Make a small opening in each cooled cream puff and pipe in the chilled coffee pastry cream.