Preheat the oven to 200°C (390°F) and line the baking tray with baking paper.

Add 120 ml milk, 50 g butter, and 1/2 teaspoon granulated sugar to the saucepan.

Bring the milk mixture to a full boil over medium heat.

Add 70 g all-purpose flour all at once to the boiling mixture.

Stir vigorously until the dough forms a smooth ball and pulls away from the sides of the saucepan.

Transfer the choux dough to the mixing bowl.

Let the choux dough cool for about 10 minutes until warm rather than hot.

Add 1 egg to the cooled dough and stir until completely incorporated.

Add the remaining eggs one at a time and mix after each addition until the batter is smooth and glossy.

Fill the piping bag fitted with the round piping tip with the choux batter.

Pipe 6 evenly sized choux mounds onto the lined baking tray.

Bake the choux buns at 200°C (390°F) for 15 minutes without opening the oven door.

Reduce the oven temperature to 180°C (355°F) and bake for 15 more minutes until puffed and golden.

Cool the baked choux buns completely on the baking tray before filling.

Slice each cooled choux bun horizontally with the knife.

Scoop about 38 g ice cream into the bottom half of each choux bun.

Drizzle about 10 ml warm chocolate sauce over each ice cream-filled choux bun.

Place the choux bun tops over the filling and serve immediately.