I make several versions of this stuffed French bread, and find it a very handy technique for feeding a large group of people. The loaves can be stuffed in advance, but to serve them hot, be sure to allow extra time at a lower temperature if you begin with a chilled loaf. This is also an excellent picnic item - just be sure to keep it chilled until ready to slice and eat. And be sure to take along plenty of extra Dijon mustard. Using a food processor, make bread crumbs from the inside of the loaf and set them aside, along with the ends of the loaf.
S aute the onion in a little olive oil until it is soft and transparent.
Add the sausage or lamb and saute it with the onions, using a fork to keep it crumbly. When it is nearly done, add the garlic and saute for another two minutes. Remove from the heat and cool slightly. Toss the mixture together quickly and lightly. Season with salt and pepper and let cool until it is easy to handle.