To give this Southern spin on fish curry an upgrade, seek out Simmons catfish, raised in aquifer-fed ponds in the Mississippi Delta. Visit simmonscatfish.com for information on where to purchase.
Combine chiles, peppercorns, cumin seeds, and coriander seeds in a dry skillet. Cook over medium, stirring often, until fragrant, about 2 minutes. Place toasted spices in a blender; add 1/4 cup water, garlic, turmeric, and 5 curry leaves. Process until a thick paste forms, about 1 minute, adding more water, 1 tablespoon at a time, if needed to blend smoothly.
Heat oil in a large skillet over medium-high. Add onion, 1/2 teaspoon salt, and remaining 5 curry leaves. Cook, stirring often, until onion is translucent, 4 to 6 minutes. Stir in spice paste, and cook, stirring occasionally, until onion is browned, about 6 minutes. Stir in coconut milk, and bring to a boil. Reduce heat to medium-low, and simmer, stirring occasionally, until sauce is thick enough to coat the back of a spoon, about 25 minutes. Stir in lime juice and remaining 1 1/2 teaspoons salt.
Heat 1/4 inch of oil in a large skillet over medium-high to 350°F. Stir together lime juice, turmeric, chile powder, salt, ginger, and garlic in a medium bowl. Add fish, and toss to evenly coat. Working in 2 batches, fry fish pieces in hot oil until golden brown and just done, about 1 minute and 30 seconds per side; drain on paper towels.
Add fried fish to curry, and serve over basmati rice with lime wedges and kachumber (an onion, tomato, and cucumber) salad.