In a flameproof casserole or Dutch oven fry the bacon over a moderate heat until it renders its fat. Transfer the bacon with a slotted spoon to a small bowl. Fry the monkfish chunks in the bacon fat until golden, about 5 minutes. Remove the pan from the heat and pour in the Cognac. Cover and leave to stand for 10 minutes. Bring the Cognac to a boil over moderate heat and stir in the red wine, bacon and bouquet garni. Reduce heat and simmer for 20 minutes. Season with salt and pepper. Melt 1/4 cup butter in a frying pan and cook the onions until golden, stirring frequently for 5 minutes. Stir the mushrooms into the monkfish mixture. Cook for 15-20 minutes. In a small bowl beat together the remaining 2 tablespoons of butter and the flour to obtain a paste. Drop this mixture 1 teaspoon at a time into the monkfish mixture and boil until thickened. Remove the bouquet garni before serving.
