Cut cod into 1 1/2-inch thick steaks. Pat dry. In a large skillet, heat the olive oil, and 2 tablespoons butter over medium heat. Saute each steak for 4 minutes on each side. Remove fish from pan and keep warm.
Place the onions in the skillet and saute until brown. Add the wine and chicken stock and season with salt and pepper. Continue cooking until volume is reduced by 1/2. Return fish to skillet and cook for 2 minutes over medium heat. Remove fish and place on a warm platter.
In the skillet, whisk in the remaining butter. Add the julienned gherkins, capers, and chopped parsley. Spoon the finished sauce over the fish and serve.
Recipe courtesy of Chanticleer, Nantucket, Massachusetts