Snapper with margarine

3 tablespoons canola oil 2 tablespoons unsalted butter or 2 tablespoons unsalted margarine 1 large red onion , thinly sliced 1/2 large Spanish onion , thinly[...]

6 pounds red snapper fillets or whole fish 24 each oysters 6 each celery stalks chopped 1 each shallots bunch, chopped * 1 tablespoon parsley leaves chopped 2[...]