Preheat oven:
Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Make the dough:
In a saucepan, combine butter, water, salt, and sugar. Bring to a gentle boil, then stir in flour all at once.
Form the paste:
Stir constantly until the dough pulls away from the sides of the pan and forms a ball. Remove from heat and let cool slightly.
Add eggs:
Beat in eggs one at a time until the dough is smooth, glossy, and pipeable.
Pipe and bake:
Pipe small mounds (about 1½ inches wide) onto the baking sheet. Bake for 20–25 minutes, until golden and puffed.
Cool and fill:
Allow puffs to cool completely. Slice in half and fill with vanilla pastry cream or ice cream.
Prepare ganache:
Heat heavy cream until hot but not boiling. Pour over chocolate chips, let sit for 1 minute, then stir until smooth and glossy.
Assemble:
Drizzle the chocolate ganache over filled profiteroles and serve immediately.