A question about a recipe: James Peterson's Baked Fish Fillets with Butter and Sherry

Tarragon or perhaps sorrel.

My favorite herbs with white-fleshed fish are summer savory, chervil, flat leaf parsley. The fish is delicately flavored, so many of the herbs we so often reach for would overpower that delicate flavor. I choose different herbs with oily fish.

I always like thyme with sherry, and it also works with white fleshed fish (e.g., in a fish chowder.) So maybe throw a few small sprigs in the pan - it will flavor the butter that's spooned over the finished fish.

I agree with the delicacy of the fish and as the recipe author states, parsley is a great idea to finish the dish.