Complete tosh, as ever, golfpro/Airpocket.
There is no need to contextualise the time of an “immediate” action as it is, by its very nature, already contextualised. Therefore the “once” as originally written, or the “when” suggested as an alternative by you, is superfluous. As I stated in my original post.
Enjoy your tea; I am looking forward to flapjacks today.
What time are the G&Ts poured in the FlyingChinaman household?