Preheat oven to 375F. Arrange cubed bread in a single layer on a large baking sheet, toast in the center of the oven for 20 minutes, stirring halfway through. Reserve.
Set a large frying pan over medium-high heat, add sausage meat and crumble until no pink remiains, about 5-7 minutes. Reserve,
Reduce heat to medium-low, melt butter, add celery, leek, apple and mushrooms, season with salt. Cook for 6-8 minutes or until softened.
Combine toasted bread with celery mixture, sausage and herbs in a large bowl. Add 1 cup of broth and stir to combine.
Dump into a 9x13" baking dish, pour remaining 1 cup of broth overtop. Bake in the centre of the oven for 35-45 minutes.