Combine the flour and 1 teaspoon of the Essence in a shallow bowl. Season the fish with the salt.
Heat the vegetable oil in a large heavy skillet. Dredge two of the fillets in the flour, coating evenly, and shake to remove excess flour. Fry the fillets until golden brown, about 4 minutes on each side. Remove with a slotted spatula and drain on paper towels. Repeat with the remaining fish. Season the fillets with the remaining 1/2 teaspoon Essence.
Mound equal amounts of the potato salad in the centers of four serving plates. Lay one catfish fillet on each, top with a dollop of tartar sauce, and serve.
Yield: 4 servings