Tilapia is a simple fish that is best cooked simply. When frying, stick to the fundamentals: Pan-searing, pan-frying or deep-frying -- all similar methods that differ mainly in fat level: Use a scant amount of fat, and you're pan-searing; use about 1 inch of fat, and you're pan-frying; use 3 inches or more, and you're deep-frying. Use high-heat oil for pan- and deep-frying -- canola, soybean, sunflower -- as it must withstand at least 400 F without smoking heavily. You can use whole butter for basic pan-searing.
Always season tilapia with kosher salt and freshly ground black pepper -- use spice rubs, herb crusts and marinades when you want something more. Herb crusts and spice rubs -- both made by dredging the tilapia fillets heavily in dried spices or freshly chopped herbs -- crisp during pan-searing and form a golden-brown, aromatic crust. For the marinade-lover, mix 1 cup of olive oil with 1 tablespoon of lemon juice and season the blend to taste; marinate the filets between 2 and 8 hours.
To pan-sear, add a couple tablespoons of fat to a saute pan and warm it over medium heat for 3 or 4 minutes. Cook the fillets for approximately 4 minutes on each side.
You have to deep-fry breaded and battered tilapia to get the all-over browning and crispness you're looking for. To make a basic tilapia batter, mix equal parts flour and water or milk along with salt and spices to taste. To bread tilapia, dredge it in seasoned flour, dip it in beaten eggs and coat it with breadcrumbs.
Heat about 3 inches of frying oil in a tall, heavy-bottomed pan over medium heat. Check the temperature with a high-temperature digital thermometer after 3 or 4 minutes: It should measure between 325 and 375 degrees Fahrenheit. Lay the breaded or battered fillets in the oil and fry them for about 5 minutes.
Preparing a whole tilapia for cooking is a technique unto itself, but if you purchase the fish cleaned with the head and tail removed, you'll have minimal prep, and it will fit comfortably in a 12-inch skillet. Stuff the empty space in the belly with herbs and lemon slices -- you need the cavity filled but relatively flat -- and slice it through the skin at an angle three or four times on both sides. Next, fry the tilapia in 2 or 3 tablespoons of fat over medium heat until it reaches 145 F in the center.
When you place fillets in the oil, lay them away from you to prevent backsplash. If you're working with deep oil -- 3 inches or more -- use a heavy pan with a thick bottom and tall sides, at least twice the depth of the oil. Use a slotted spoon to lower fillets into deep oil, and use tongs to turn them and pull them out when ready. Use a high-heat thermometer to check oil temperature and an instant-read meat thermometer to check the fish temperature: Seafood is ready when it reaches 145 F in the center.