Start by taking out the crab meat. The shell is soft and is easily cut with scissors. Place the crab meat on a plate, cover and refrigerate. Reserve the shell. In a medium pot, heat ½ tablespoon butter over medium high heat. Add crab shell, shallot, bouquet garni, wine and water. Let simmer for 20 minutes. Strain, discard solids, return stock to clean pot. Bring to a boil and reduce by half. Add carrots, cauliflower and peas, cover, and boil until almost tender. Add salt and pepper to taste. Keep warm.
In a hot skillet, heat 1 tablespoon butter. Sprinkle cod with flour, salt and pepper. Place in skillet and fry until golden brown on both sides and flesh starts to flake easily when poked. Season crab and fry until golden brown on both sides, 1 to 2 minutes on one side, 1 minute on the other.