1. Stir together first 10 ingredients in a small bowl. Set aside.
2. Heat oil in a wide, deep, ovenproof skillet over medium-high heat. Season the cod fillets with salt and pepper, and cook 4 minutes. Turn fillets over; cook 1 minute.
3. Spoon 1 tablespoon butter mixture over the top of each fillet; transfer skillet to oven, and bake at 450° for 2 minutes or until fish is just cooked through and opaque in the center.
4. Add any remaining butter to pan, and let melt, stirring with juices in pan; spoon over fish, and garnish, if desired. Serve immediately.