If you've been to the frozen foods section of your local supermarket recently, you might have seen frozen swai fillets. Consumer Reports recommends this fish, an Asian relative of the catfish, as an economical relative to pricey cod and trout. However, taking full advantage of this inexpensive, mild-flavored white fish requires a little information.
Thaw your fillets by filling a cake pan with cold water, placing the fillets in a gallon-size zip-top baggy and placing the bagged fish in the water. Change the water every 20 minutes, turning the fish over each time, until the fish is thawed. Cooks Illustrated Magazine recommends this thawing technique because it is convenient and produces the same results -- when used with thin fillets -- as refrigerator thawing.
Remove the fish from the plastic baggy and place on a clean cutting board. You may notice a dark stripe running down the side of your fish fillets. This is the bloodline, and it has a stronger, somewhat muddy flavor you may not like if you're not used to catfish. To remove it, simply cut it off with a sharp knife. A chef's knife works best for this but any kitchen knife will work.
Blot the fish dry with paper towels and sprinkle with salt and pepper. Blotting fish dry helps it cook evenly, and seasoning before cooking allows the salt and pepper to work deeply into the flesh.
Place a nonstick skillet over medium-high heat and add the butter. Swirl the skillet to distribute the butter. The butter is ready to cook with when foaming subsides and the butter takes on a slightly nutty aroma.
Add the fish to the butter and cook without moving the fish until it turns white and flaky and develops a slight crust, two to three minutes. Gently flip the fish using a fish spatula or pancake turner, being careful not to break the fillets apart. Cook for another two to three minutes or until the fish is white and flaky, but not dry, all the way through. Serve hot with lemon slices.