1. Roll the beef cubes in flour and brown them on all sides in a skillet over high heat in four tablespoons each of the butter and olive oil.
2. Sprinkle the meat with salt and pepper, pour the cognac over it and ignite. When the flame dies, transfer meat to a three-quart casserole.
3. Preheat oven to moderate (350° F.).
4. To the skillet add the bacon, garlic, carrots, leeks, chopped onions and two tablespoons chopped parsley. Cook, stirring, until the bacon is crisp and the vegetables are lightly browned. Transfer to the casserole with the meat and add the bay leaf, thyme, Burgundy and enough water to barely cover the meat. Cover and bake one and one-half hours.
5. Prepare a beurre manie by blending one tablespoon each butter and flour and stir into the casserole bit by bit. Return the casserole to the oven and continue cooking two to three hours longer.
6. Brown the small onions in two tablespoons butter with a dash of sugar. Add a little water, cover and cook until the onions are almost tender.
7. Saute the mushrooms in two tablespoons each of the butter and oil until lightly browned on one side. Sprinkle with lemon juice and turn to brown the other side.