Place the beef bones on a baking tray and season with salt. Roast at 180c/350f for 30 minutes. Turn them over and roast for another 30
Then in a big sauce pan, add the bones with the onions, celery, rosemary, shallots, carrots, garlic and black peppercorns and fill with water. Put onto boil and leave to simmer for at least 6 hours. The longer the better
Slice your onions and add to a pan with the butter. Keep stirring until they are nicely caramelised (roughly 30 minutes). Then season with salt and pepper add the flour and stir well. Deglaze the pan with white wine. Make sure you strain your beef stock and then add to the onions. Season to taste and throw in a couple of bay leafs. Leave to simmer
Slice the baguette and drizzle over olive oil. Bake at 180c /350f until nice and crisp (10-15 mins). Then take a garlic clove and rub on each slice.
In a bowl, add the soup, then some cheese followed by the croutons and then plenty more cheese. Stick under the grill until golden brown and melted.