The Fish lyrics

‘First the fish must be caught.’
That is easy: a baby I think could have caught it.
‘Next, the fish must be bought.’
That is easy: a penny, I think, would have bought it.

‘Now cook me the fish!’
That is easy, and will not take more
than a minute.
‘Let it lie in a dish!’
That is easy, because it already is in it.

‘Bring it here! Let me sup!’
It is easy to set such a dish on the table.
‘Take the dish-cover up!’
Ah, that is so hard that I fear I’m unable!

For it holds like a glue-
Holds the lid to the dish, while it lies in the middle:
Which is easiest to do,
Un-dish-cover the fish, or dishcover the riddle?