Hmm the old touching cloth leading to unsinkable Molly scenario.

This may take some time.

First thing ventilate the dangerzone nothing ruins romance more than the pong of poo.

Cover the beastie with a reasonable membrane of tissue and grit your teeth, clear your mind and find an inner calm.

Then push that bugger so it vanishes down the U-bend.

Then flush.

It may take time and if so wash your paws while the cistern fills.

If the basin has filled with water, wait a bit, access the situation the water may find a way through the wall of ex-food.

Don't Panic!

If the water does drain flush again (you may get lucky and have unblocked the pipe).

If not put bring down your coat.

Evacuate to a nice restaurant and make out that this was your plan from the very beginning but you wanted to keep it as a surprise.

Get a plumber to sort the mess out in the morning.