Sourdough Stuffing with Mushrooms, Apples, & Sage

loaf crusty sourdough bread, cut into 1/2-inch cubes (about 11 cups)

unsalted butter

large onion, diced

ribs celery, chopped

fresh cremini mushrooms, sliced

Granny Smith apples, cored and chopped

vegetable broth

large eggs

chopped fresh sage leaves

fine sea salt

freshly ground pepper