Hi Ziggy:
For Sesame or Poppy Seeds you can slightly moisten the fish with water, soy sauce, or just the natural juices if it is a moist fish.
Coat the Mahi, Salmon, Grouper, (whatever fish you are using)
until enough seeds cover one side of the fillet. I will place the fillet seed side up into a small amount of a ginger soy sauce (unthickened), Lemongrass broth, etc....(using one type that goes with the dish) and baking in a 450 degree oven until done.
You can toast the sesame seeds in advance, or purchase this way in a good Asian market.
The times will vary with the type of fish, and the thickness......approx. 7 to 10 minutes.
If I am using nuts......I will chop the nuts, but not turn to dust......add a small amount of flour, salt if needed.
Dust in seasoned flour----then light amount of eggwash, then the nuts.........make sure the nuts cover the fish---you can even pack it with your hands.
Now the coated fillet can be seared on one side in a non-stick pan with a small amount of oil. Sear on one side, and transfer to a baking dish that is lightly oiled, or sprayed with a non-stick type spray. Bake in a 400 degree oven, or even slightly higher until the nuts are a golden brown, and the fish is firm to the touch.
Now Hazelnuts (Filberts) work best if you roast them first, cool, then crush. I think you get more flavor out of them.
A good way to crush them for a small amount. put in a small freezer bag, and hit them with the side of a mallet. Oh, yes sometimes the bag will break, but you will get the hang of it.
Or, if you have a food processor, that works great.
I make a Hazelnut Encrusted Breast of Chicken in a Frangelica Cream this way. Except I will brush the chicken with frangelica and (skip the flour, eggwash) dredge the breasts in the hazelnut mixture.
Hope this helps,
Chef Nosko
Boston, MA