The best way would of course be to close up the pen so the crow(s) can't get in at all. You probably have more than one.
Having said that, crows ( and ravens) are extremely smart and they actually pass along information to the the rest of the flock so if you eliminate a particular crow, you will have others who have "heard" about the free meal. I know that sound unbelievable, but its true.
I love having our crows and ravens around (although they are not stealing eggs) as when they are nesting in the area, they make the best babysitters for the hens as they will chase off any and all hawks.
good luck.