MURE

The Ugly Duckling of the sea
Had Zero desirability

Until a good cook
Gave it a whole new look

Ugly did be
The Beautiful Swan of the sea

It needed a good bath
And some basic math

How do I know?
Just read below
↓

Let CL = Clams
MU = Mussels
and
RE = An excellent REcipe
and
CL + RE = An excellent clam recipe

Then substitute MU for CL
and
MU + RE = An excellent mussel recipe