How to Make It
In a medium saucepan, cover the black-eyed peas with 2 inches of water and bring to a boil. Simmer over low heat, stirring occasionally, until the peas are tender, about 45 minutes. Drain the peas.
Meanwhile, in a small bowl, cover the dried shrimp with hot water and let stand until softened, about 30 minutes. Drain and coarsely chop the shrimp.
In a large bowl, combine the olive oil with the lime juice, cilantro, scallions, shallot, tomato, garlic and jalapeño. Fold in the black-eyed peas and chopped dried shrimp and season with salt and pepper. Let the black-eyed pea salad stand at room temperature for about 15 minutes, stirring once or twice.
In each of two large nonstick skillets, heat 1 tablespoon of the vegetable oil until shimmering. Season the mackerel fillets with salt and pepper. Add them to the skillets and cook over high heat until lightly browned, about 3 minutes. Turn the fillets and cook until just opaque throughout, about 2 minutes longer.
Using a slotted spoon, scoop the black-eyed pea salad onto 4 plates and set the sautéed mackerel fillets on top. Drizzle any remaining dressing from the salad around the plates and serve.
Dried shrimp are available at Asian markets in a variety of sizes and forms. Choose headless shrimp that are still slightly pliable; they shouldn't crumble when pressed.