Preheat the oven to 400 degrees. Over a large cutting board, cut the bread into small cubes.
Put cubes of bread onto a sheet pan, then toss with the Olive Oil. Bake for 20 minutes, tossing around halfway through.
In a large frying pan, combine the sausage, leeks, onion and celery. Cook over medium heat until they are all cooked through, sausage is completely cooked and vegetables are completely soft. Add a bit of oil if it goes dry.
Add the salt, thyme, parsley, sage and white wine (or broth) to the sausage/ vegetable mixture. Let cook for another ten minutes or so, stirring often, over medium heat to deglaze the pan, and let all the flavor come together.
In a large mixing bowl, combine the sausage/vegetable mixture with the toasted bread cubes. Toss to combine. Then add 2 to 3 cups of chicken broth. You want the bread cubes to be moistened but not crazy soggy.
Empty the contents of the large bowl into a greased 9x13 inch baking dish. Spread evenly, then top with 4 tablespoons of butter. Put it into a 400 degree oven to cook for 30 minutes. Cover with foil if needed for the last ten minutes, or if some of the bread cubes are browning too dark.
Remove from oven and serve immediately!