In a large nonstick skillet, heat the olive oil until shimmering. Season the fish with salt and pepper and dust all over with 1 tablespoon of the flour. Add the fish and garlic to the skillet and cook over moderately high heat until barely golden, about 2 minutes. Sprinkle the remaining 1 tablespoon of flour over the fish. Turn the fish and add the peas, half of the parsley, the wine and the cockles. Cook, shaking the pan occasionally, until the cod is almost cooked, about 4 minutes. Add the shrimp, tucking them into the liquid. Cover and cook for 2 to 3 minutes, until the shrimp are pink and curled and the cockles have opened. Sprinkle with the remaining parsley and serve in shallow bowls.