For the Bean Ragout: Soak the beans in water overnight. Drain and reserve.
In a saucepan, heat 2 tablespoons of oil and saute the pancetta until lightly browned. Add the onions, carrots, and celery and saute until lightly golden brown, about 5 to 8 minutes. Add the reserved beans, vinegar, stock, bouquet garni, and salt. Bring to a boil, then lower to a simmer. Cook until just tender, about 40 minutes.
For the Chanterelles: In a heavy skillet, heat the remaining 2 tablespoons of olive oil. Add the chanterelles and saute for 5 minutes or until golden brown. Add the tomatoes and saute another 3 minutes. Taste and adjust seasoning with salt and pepper.
Vidalia Onion: In a medium saute pan, over high heat, saute onions in olive oil until crisp and golden in color. Reserve.
For the Sauce: In a saucepan, over medium heat, add oil. When oil is hot, add shallots and saute until translucent. Deglaze with sherry and reduce in half. Add veal stock, cream, and some of the bean cooking liquid and continue to reduce until thick. Taste, and adjust seasoning with salt and pepper.
For the Fish: Season fish with salt and pepper. In a non-stick saute pan, heat the olive oil until smoking. Sear fillets, skin side down for 3 minutes and golden in color. Add rosemary sprigs to oil. Turn fish over and cook on other side until translucent.
To serve: divide the onions and place in center of each serving plate. Add the bean ragout on the side and place the seared fillet in center on top of onions and bean ragout. Top with the chanterelles. Coat with sauce.