From America's Test Kitchen
Blackened fish is usually prepared in a cast-iron skillet, but it can lead to one smoky kitchen. We thought we’d solve this issue by throwing our fish on the barbie (it works for more than just shrimp, right?). Unfortunately, this move created a host of other problems, including fish stuck to the grate, the outside of the fish being way overdone by the time the flesh had cooked through, and the skin-on fillets curling midway through cooking. We were done with the smoke—and were ready for our fillets to have a dark brown, crusty, sweet-smoky, toasted spice exterior, providing a rich contrast to the moist, mild-flavored fish inside.
The curling problem was easy to fix. We simply needed to score the skin. The sticking solution proved more difficult, but the answer turned out to be a trick that we’d used before to grill salmon fillets—setting a big piece of heavy-duty foil on the grill. By placing a large piece of foil over the grate while it preheated, we made the grill superhot. This heat incinerated all the nasty gunk on the grate and gave us a really clean surface on which to cook the fish; oiling the grate with a heavy hand didn’t hurt, either. Finally, to give the fish its flavorful “blackened but not burned” coating, we bloomed our spice mixture in melted butter, allowed it to cool, and then applied the coating to the fish. Once on the grill, the spice crust acquired the proper depth and richness while the fish cooked through.
If using fillets that are 1/2 inch or thinner, reduce cooking time to 3 minutes per side. If using fillets that are 1 inch or thicker, increase cooking time on second side by 2 minutes, moving the fish to the cooler side of the grill after the second side has browned. If you cannot find red snapper, striped bass, halibut, and catfish can be substituted. Making the slashes in the skin requires a sharp knife. If your knife isn’t sharp enough, try cutting through the skin with a serrated knife. However, cut in one direction (don’t saw) and be careful not to cut into the flesh. If you choose not to eat the skin, be sure to remove it after cooking rather than beforehand. Serve fish with lemon wedges and our Rémoulade or our Pineapple and Cucumber Salsa with Mint.