1 quart buttermilk
1⅓ pounds fresh fish fillets (such as catfish, flounder, trout or grouper), cut into serving pieces
1 cup self-rising flour, seasoned with salt, pepper and a pinch of cayenne
1 scant cup vegetable oil, peanut oil or lard, or more as needed
1 tablespoon bacon grease or butter
Lemon wedges and tartar sauce, homemade (recipe follows) or store-bought, for serving
Homemade Tartar Sauce
1 cup mayonnaise
¼ cup finely chopped dill pickles or sweet pickle relish
2 green onions (scallions), white and firm green parts, minced
1 tablespoon snipped fresh dill
Fresh lemon juice to taste (start with 2 teaspoons)
Salt and ground black pepper to taste
Cayenne or Dijon mustard (optional)
1. Prepare the Fish: Pour some of the buttermilk into a shallow baking dish and add the fish fillets; add more buttermilk as needed to completely cover all the fillets. Let the fillets rest for half an hour.
2. Preheat the oven for 200°F to keep the first batch of fish hot. Warm a serving platter in the oven. Have ready a baking rack set on top of a baking sheet for draining the fish.
3. Put the seasoned flour on a plate or a small platter. One at a time, shake any extra buttermilk off each fillet and dip it into the flour on both sides, making sure it is covered, but not too thickly, then shake off any extra flour and lay the fillets on wax paper.
4. Fry the Fish: Heat a heavy skillet (at least 10 inches wide) over medium-high heat. When it’s hot, add the oil or lard to a depth of ¼ inch, then add the bacon grease or butter. When the fat is sizzling, drop in half the fish. Fry until crisp and golden on the bottom, about 3 minutes, or longer for thicker fillets, then turn the pieces—just once!—with a long, wide spatula and let crisp on the bottom. Drain on the rack and keep warm—still on the rack—in the oven until all the fish is cooked. Add more oil or lard to the pan if needed to fry the second batch, and make sure it’s hot before adding the fish.
5. Make the Tartar Sauce: Stir the mayonnaise, pickles, scallions, dill, lemon juice, salt and pepper together in a small bowl. Let it sit for a bit to mellow and then taste it—you may want to add more lemon juice or some cayenne or Dijon mustard.
6. Serve the fried fish on a platter surrounded with lemon wedges, with tartar sauce on the side.