In a clean box, scoop out 1/3 of the ready vanilla ice cream.
Level it with a spoon.
Pour 1/2 of the chocolate sauce in big drops over the vanilla ice cream.
Do not level it.
Gently spoon out more ice cream over the chocolate sauce, taking care not to disturb the chocolate sauce.
Level the ice cream gently.
Pour more chocolate sauce over the ice cream.
Gently spoon out the left over ice cream.
Freeze for 1-2 hours.
A white ice cream with lovely chocolate ripples will be seen when you serve the ice cream.