Biscuit M is very hard

Why is this biscuit Biscuit M
when others never shed a crumb?

My biscuits run from A to Z.
A little boy bit Biscuit L
broke the biscuit
bent his head.

Biscuit K I bit myself
it tasted rough and gritty.
But who’d eschew infinity
in a crumble-quaking city?
Besides, that biscuit’s taken
consuming its own past.
And of all the biscuits I have left
M is never lost.

Don’t put it to your mouth, I crave:
guard that biscuit from your
teeth and you will find
you’ll never try to bite it and
you’ll always have an M upon your mind. 

© Dennis List