Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.

Melt the butter in water over medium heat, then bring to a rolling boil.

Reduce heat to low and add flour all at once. Stir vigorously until the dough pulls away from the sides.

Let the mixture cool slightly before adding eggs to prevent scrambling.

Beat in the eggs one at a time until the dough becomes smooth and glossy.

Drop walnut-sized spoonfuls of the dough onto the prepared baking sheet, spacing them apart.

Bake for 20 to 25 minutes until golden and dry, avoiding opening the oven during the first 15 minutes.

Cool completely on a wire rack before filling.

Whisk the pudding mix with cold milk until smooth, then add sour cream and blend until thick.

Refrigerate the filling for at least an hour before using.

Slice cooled puffs in half and fill generously with the prepared filling.

Dust with powdered sugar right before serving.