I removed the head, tail, and bones (mostly) as the kiddo is on the squeamish side. My fish was on the small side, so adjust accordingly for your needs.
For the Filling:
A combination of dry breadcrumbs, crackers (I had vegetable Breton crackers) about a tablespoon of finely minced preserved lemon peel (or the grated zest of a lemon if that's what you have), 2 finely minced garlic cloves, 1/4 teaspoon dried tarragon (use more if you like, mine was pretty recently dried and quite strong) Salt/pepper, and about 1 cup of chopped, fresh spinach leaves.
You're looking at me funny, so I'll explain- the spinach will give off just enough moisture to soften the breadcrumbs without creating a mush. You don't need to precook the greens. Now stop looking at me funny.
I use foil to bake fish, but if you're handy at folding parchment, feel free to use it. Oil the foil (rhyme time!) with some olive oil so your fish won't stick. Place the fish on the centre of the foil, fill with the bread/spinach mixture. Drizzle with a bit of olive oil, then seal in the pouch. Bake at 450 degrees F. for about 20-25 minutes.
With my extra spinach I made a saute of red pepper and sweet onions tossing in the spinach at the last.
For the Barley:
1 cup medium pearl barley
water to cover
Soak 30 minutes. Rinse well, drain. Place in saucepan with enough vegetable stock to cover. Bring to a boil. Reduce heat to simmer, cover and cook until most of the liquid is evaporated-about 40 minutes. Drain, rinse well under cold water to remove excess starch. Toss with about a tablespoon of zataar. Reheat, or serve at room temperature.
*I make a sumac free zataar due to allergy. Mine is equal parts marjoram and oregano with 1/2 part thyme, a few fennel seeds, and a few tablespoons of toasted sesame seeds. Grind it all lightly together, and store in the fridge.