The "won't eat what Daddy fixes for dinner cure" Is there one?

Gavin is going through a VERY picky eating phase and it's driving us insane.  Brady has been so kind as to fix dinner every night and Gavin won't eat anything.  He pushes the plate away and makes snide comments about how the food is yucky throughout the meal (because we make him sit and watch us eat even if he's not going to eat).  Last night, he did not eat dinner because we refused to fix him something else.  The rule is, if you try it and decide you don't like it, Mommy or Daddy will fix you something else.  If you don't try it, you don't eat.  Gavin would not try it, so he did not eat.  Tonight he at least tried it but ended up with a PB sandwich.

What can we do to fix this?  My mom thinks we are mean to not just fix what he wants.  I realize that when I was growing up, she had to fix food I'd eat because of the diabetes and insulin:carbohydrate ratio dilemma, but we don't have that issue with Gavin.  I don't want every person having a different meal each night.  That is waaaaaay too time consuming and quite ridiculous.  However, Gavin is so skinny, I don't think he should be skipping meals even if it is to teach him a lesson.

What can we do?

Oh the joys of parenting...