Sardine fillets aren't all that common as a dish in the United States, but they certainly can and should be. Sardines are plentiful in the wild, so they're a cheap and sustainable option. They're also packed with healthy omega-3 fatty acids, vitamin D and other essential nutrients. In fact, although salmon and tuna are famous for their omega-3 fatty acid content, sardines have more per ounce. Prepare sardine fillets using just about any of your favorite fish recipes. Because they're small and thin, they will cook quite quickly no matter how you're making them.
Thaw your sardine fillets if they're frozen; otherwise, they won't cook evenly. For the best results, thaw them in the refrigerator for 12 to 24 hours. If they're sealed in a leak-proof package, you can defrost them more quickly by submerging them in cold water for about an hour. Change out the water every 30 minutes with colder water. Sardine fillets are too small and delicate to defrost in the microwave; they'll start to cook and end up rubbery by the time you're done preparing them.
Rinse the sardine fillets off, making sure to clear them of any bits of scale that may be stuck to the flesh. Pat them thoroughly dry with paper towels.
Flavor the sardine fillets to taste. Brush both sides with cooking oil or melted butter. Sprinkle on a bit of salt, pepper and a favorite dried herb, like thyme, oregano or rosemary, for a basic preparation. Minced garlic complements most fish dishes, too. Or, try lemon juice and dill; more potent seasonings like paprika, turmeric or a little chili pepper powder; a Moroccan-style preparation using paprika, coriander, cilantro, parsley, garlic and lemon juice; an Asian-style approach using soy sauce or tamari, garlic, ginger and chopped scallion; or just Cajun blackening seasoning. Your options are practically limitless.
Pan-sear sardine fillets. Preheat a large skillet over high heat, then add cooking oil to coat the bottom. Heat the oil, then add the sardines skin-side down. Press firmly on the fillets with your spatula for a few seconds to prevent curling. Sear for about one minute, until the fish slides when you shake the skillet and the underside is nicely browned. Turn the sardines and sear the other side for about another minute, until the exterior is nicely browned, the flesh is opaque throughout and it flakes easily with a fork.
Grill the sardine fillets if it's outdoor cooking weather. Scrape your grill clean, then grease the grates with cooking oil. Preheat to medium-high heat. Place the sardines on the grill skin-side down. Grill them for about two minutes, until the underside is nicely browned. Turn the fillets carefully with a spatula and continue grilling for about about another two minutes. The sardines are done when their meat is evenly opaque and flakes easily with pressure from a fork.
Broil the sardine fillets if you don't want to go out to your grill. This is a similar dry cooking method that's even less involved. Remove the broiler tray from your oven, line the bottom with aluminum foil, grease the foil with a little cooking oil and preheat the broiler for 10 minutes. Slit each fish's skin a few times to prevent curling and shrinkage. Place the fillets on the foil skin-side up and put the tray into the broiler, positioning the sardines 2 inches from the heating element per 1/2 inch of thickness. Turn the fillets after about two minutes, then continue broiling for about another two minutes. Remove the fish when its flesh is flaky and opaque through to the center.