Oyster Stuffing with Chestnuts and Sausage

1 loaf White Bread (bottom crust removed, cut into 3/4in cubes)11 ounces sausage of your choice (sliced diagonally)2 tbsps olive oil (if needed)3 cups shiitake mushroom caps (thinly sliced)salt and pepper (to taste)5 slices bacon (thinly cut, minced)3 cups leeks...