In a large skillet, over medium heat, fry the bacon until crispy, about 3 to 4 minutes. Using a slotted spoon, remove the bacon and drain on a paper-lined plate. Set the bacon aside. Stir the fat into the flour and make a medium brown roux, the color of peanut butter, by stirring constantly for 8 to 10 minutes. Stir in the onions and saute for 3 minutes, or until the vegetables start to wilt. Add the mushrooms and continue to cook for 2 minutes. Season with salt, pepper, and cayenne. Add the garlic and sherry and cook for 2 minutes. Stir in the tomatoes and chicken stock and bring the liquid to a boil. Season the quail with salt, pepper, and cayenne. Add the quail to the mixture and simmer for 30 minutes, basting the quail every 10 minutes. Stir in the lemon juice and parsley. Serve the quail with the Jerusalem Artichoke and Potato Au Gratin and garnish with the reserved crispy bacon.